I have owned the XBA-3 and XBA-1 beforehand and now I own the 1 and 4 only. As far as multi-driver IEMs go I don't think you'll find a more consumer oriented set than the Apple In-ears and the XBA line.
The package includes the earphones, the same fitting kit included with all the rest from the line (4 sizes of standard universal tips, and 3 sizes of "hybrid" tips that have a ring of foam inside the flap of the tip to provide more isolation), magnetic fake leather carrying case like the XBA-3's, and a cord manager. This is pretty much what you would expect for the price and is not as impressive when compared with something like the XBA-1 which are 1/4 the price and include pretty much the same goodies (except for a pouch instead of a case).
The XBA-4 themselves share the looks of the family: glossy paint in sober colors with silver accents, a great stress relief (not found in the XBA-1), semi-flat wire, and a nice L headphone jack. The cord is semi-flat, asymmetrical, and while it is thin and feels fragile, it is very easy to untangle. It is a shame it is non-removable as it looks it would be a hassle to repair if it were to break, which is not that unlikely to eventually happen. I have found the XBA line to be extremely comfortable...except for the XBA-4. They are very large, and even when they don't seem to be that much larger than the XBA-3 (which I could wear for hours at a time), the issue is their width and not their height. They rest on the antitragus but they are so wide because of the two drivers in the middle of the assembly that they chafe my concha after some minutes; some readjustment gets the job done but if you can, try to fit them on before buying. They are heavy in comparison with other plastic IEMs, but not heavy for a 4-driver IEM and here is where the plastic construction finally makes some sense.
Having the same fit kit than the rest of the XBA line has advantages and drawbacks, the first being the super soft and comfortable ear tips. On the other side, there's an issue with the nozzle. I've heard people complain that they don't go deep into their ear canals and it makes sense since the housing is so huge. It only is a problem for me when I try to wear them with the wire facing upwards. The shape of the housing is not an issue there, but the length of the nozzle and the tip is. The isolation is just as the XBA-3's (way better than the XBA-1 but pretty much average isolators). They will work on a plane or bus for sure.
Now comes a very interesting part for this review in particular. The sound quality is an incredibly mixed bag. I can see in the other reviews that people have very mixed opinions on the sound signature, specially with the highs: some people complain about sibilance and too much sparkle while others complain about a darker sound. I have experienced both and I can only tell something for sure: they are extremely source dependent. This is, in my opinion a huge disadvantage. We all know sound is different with different sound cards, amps, DACs, phones, and so on, but headphones generally maintain a certain signature that doesn't change with the source (for example the "Sennheiser veil" or Etymotics characteristic crispness) and these do change, a lot. In general, the sources I've found to have the most negative effect on these are by far smartphones and mobile devices. They don't sound bad with these per se, but they make the XBA-4 sibilant and make the highs too sparkly, almost to the point of being piercing (Zune 80, iPod Touch 4G, Galaxy S2 (AND very low volume with this one), Galaxy S3, and Galaxy Player 4.0). I've heard this is a result of their very low impedance of 8 Ohms so in order to get the most out of these you'll need an almost 0 Ohm jack on your source (which I haven't tried yet). But when using other sources these issues are almost gone and everything changes for the better and even soundtage improves. Powering these from a Xonar Essence STX card or a FiiO E10 or E17 alone makes a great improvement.
Now I'll mention the constant sound properties of these, which I found to be extremely appealing. First the soundstage, which is fantastic! I can't believe such an open sound can come from closed IEMs. Instrument separation is really good but that's what you'd expect from multi-driver IEMs, although at times it seems as if they lacked coherence when the sounds have a very different frequency from one another; it is funny since this means congested stuff tends to sound better. The mids are very nice, but somewhat recessed (but it isn't an issue with vocals in my opinion), and while the bass is lush and very present, it is not overpowering. The XBA-4 include a super-woofer and I was a little worried about its effect on music but I was pleasantly surprised! The super-woofer doesn't overpower anything at all, but adds warmth and body to the other sounds, makes bass more present and with good extension. Highs in general (sibilant or not) are very well extended as well and work great with classical music.
In conclusion I can say I like these more than the rest of the XBA line. The XBA-3 is better with vocals but most of my music has none or little vocals so in the end the musicality of these won me over. I'm pretty used to the Sennheiser sound so a fuller sound that I hadn't found in BA drivers until now is really nice. They offer great bass while maintaining the separation and life of the other frequencies and an above average soundtage. Comparing these with the Shure SE535 I have to say the Shure have more impact in every single frequency and the Sony offer a more laidback sound. But I don't think one is inferior to the other; in fact they have share similar qualities like the separation and soundstage but with a different sound signature. In terms of construction quality the Shure SE line is the clear winner with a HUGE advantage, but I guess that's were the price difference comes from in the end. But I think neither of these is worth their MSRP considering their sound quality and construction is not that different from the cheaper models of their respective lines.
I got these from Mexico's Sony Store for a ridiculous amount of money; they were a mere $142 USD, price that was supposed to last until March 1st. Of course I got them but then the horror! Of course they were sold at that price until that date! Afterwards they were 46 USD on the online store. Yes, it is not a typo, 46 friggin USD! Of course they are sold out. It makes you wonder how much money do these really cost to make and why was sony so eager to get rid of them (my guess is the updated XBA-X0 line). About being worth their original MSRP....I think it is worth it because of all the technology stuffed inside, but not because of the sound quality which is what matters in the end so don't pay the full price.
I hope you enjoyed reading my insights and found this helpful. Happy listening!