Build, fit and other non-sound related factors:
Generally, these are built extremely well. FitEar apparently does a full acrylic injection for the IEMs or something along the lines of that, so the TG334s are very solid feeling in the hand. Honestly, they don't look that good compared to a lot of top-end CIEMs and mainstream top end IEMs (SE 846, K3003, IE800), as they are a single-shade deep translucent black with a matte black finish on the faceplate which is not too interesting to look at. You're probably not buying IEMs purely for the look, and the TG334 will appeal to people would like the "stealth luxury" concept. If you rock white Common Projects rather than red Balenciagas kicks on the daily, then these will appeal to you. The cable provided is of above-average quality bordering on excellent. They are on the slim side, have a very nice Oyaide plug, and easy to manage memory wire. However, they're a bit springy and not too soft.
Fit-wise, I'm finding them to fit very nicely. The shells are extremely big, but they sit comfortably outside the ear. The silicone tips included are pretty trash, aftermarket tips are highly recommended. People have recommended going to JVC Spiral Dots, Ortofons, Complys, Spinfits, and the whole lot. My favourite tips with these were the Ortofons, followed closely by the Spiral Dots. They just disappear in the ear with these. The TG334 do not have a very "tight" seal, but it's easy to take on and off and isolation levels are good.
For other things, the TG334s include a decent amount of accessories such as extra tips, a Pelican hard case, a soft case (which I didn't get in my example), and a cable clip. Packaging is sober, pretty reflective of Japanese sensibilities.
The TG334s are quite a sensitive IEM, my phone and laptop can get these much louder than the other IEMs and earbuds in my stable (UE 900, Xiaomi Piston, VE Monk). As an example, on my Xperia, a good listenable volume for my UE 900s are around 80%, whereas these are closer to 50% of max. They also don't hiss too much which makes them fairly easy to live with in terms of the source. Honestly, I haven't noticed too much of a difference switching between my various sources on hand (Xperia Z2, Dell 13 Chromebook, ALO Island). I found it to have great synergy with Chord Mojo.
The overall sound signature I'd classify as mostly flat with a slight uptick in the bass and tiny bit of roll-off in the treble. Bass has good weight and extension for an IEM, but it's not the quickest. Mids are very nice on these, which are good for vocals. Really lush and involving, listening to acoustic on theses connected to Chord Mojo gave me goosebumps with how much weight the vocals and guitars had.The highs are good, but not emphasized. Overall, it's a balanced, but pretty fun sound signature, and makes my UE 900s sound positively veiled in comparison.
From a soundstage and clarity front these get high marks. Sound stage is more intimate for a high-tier headphone/IEM, but I have no faults with regards to instrument separation and the overall size. They blow the Pistons out of the water (I hope they do) and compared to the UE 900, they're a bit more narrow left-right but seem deeper front-back, if that makes sense.
I do understand if a lot of this sound stuff sounds pretty fluffy, but on an overall basis, the FitEars sound pretty damn good. It's got a profile that I think a lot of people would find pleasing, and would work well with basically all genres of music. I'd say they mesh the best with acoustic and jazz which really takes advantage of the good mids and instrument separation, but EDM and pop music is also served well on these due to the good bass.
Quick comparison with Campfire Andromeda:
Ultimately, I ended up replacing the TG334s with the Campfire Andromedas as I enjoyed the more extended treble of the Andromedas more and was able to save some money in the process. The overall level of SQ is still quite close between the two. To be fair, TG334 is a pretty old IEM now nearing 4 years, so it's quite good that it's able to compare so well still to the Andromedas, which are the cream of the universal IEM crop at the moment. Here's how they compare in some key areas. Bolded is where TG334 wins.
= : equal
> : slightly better
>>> : definitively better (to me at least)
Build quality: TG334 >>> Andro (Andro's aluminum scuff easily, like TG334 connectors better than MMCX on Andro)
Cable: Andro > TG334 (Andro's litz cable very soft and pliable, TG334 cable too springy)
Included tips: Andro >>> TG334 (TG334 silicone tips are honestly awful for the price)
Other accessories: Andro > TG334 (TG334 has pelican case, but Andro has a nice leather case and a pin!)
Bass quantity: TG334 >>> Andro
Bass quality: Andro > TG334
Mids quantity: TG334 = Andro
Mids quality: TG334 > Andro (slight edge for TG334 mids, better enjoyed its lushness and holographic nature)
Treble quantity: Andro >>> TG334 (much more extended treble)
Treble quality: Andro > TG334 (extended treble has more detail)
Soundstage: Andro > TG334 (wider presentation, very close though)
Speed: Andro > TG334 (TG334 bit slow in comparison)
Clarity: Andro = TG334 (both have little/no veil in sound)
Detail retrieval: Andro > TG334 (owing to better treble)
Comfort: TG334 >>> Andro (while Andro is comfortable, TG334 is a step above)
Source "pickiness": TG334 > Andro (Andro's high sensitivity means its sound is more variable across sources than TG334 is, both sound quite good out of the latest crop of smartphones though)
After-sales service: Andro > TG334 (FitEar seems like a difficult company to get a hold of, haven't dealt with either company though)
On a scale with all the headphones/IEMs I've owned, I'd probably put them on the same level as the Audeze LCD-2s and close, but a tad behind the HD800s. Probably better than the HD 600/650s, but I haven't heard those in a while and the sound from them, while good, were a tad forgettable from my sources. My second favourite IEMs owned so far after the Andromeda, They remind me a tad of the Westone 3s I've had before regarding the fun-ness sound signature, but with better mids, soundstage and fixing all of the issues I've had on those regarding hiss and fit. If I can find a FitEar with more extended treble, I'd probably switch my Andromeda for the brand again since I prefer the build and finish on FitEars and the overall feeling of quality they bring to the table.