So, I've had these for just over a month now, giving them a lot of listening time.
I love them. Their sound is just about perfect for my ears! As I've mentioned in other threads, every time we move up on the Grado ladder, we think simultaneously that nothing will ever sound better, but also that it is definitely a step up from the one before. And that's exactly how I feel about the RS1i vs the SR-225i that I have.
The best way to describe the overall presentation and sound between the RS1i and the 225i is that the RS1 is like sitting next to the fireplace enjoying a quiet evening on a cold winter's night, while the 225 is going to the concert in the middle of the summer. They are warmer and cozier than the 225, and a good bit more detailed. Dave Brubeck and his band are really something else on the RS1. Guitars are typical (ie fantastic) Grado sound, and they don't disappoint. I actually prefer electric guitars coming from the 225, but acoustic strings are exponentially better on the RS. The bass seems more abundant from the 225, but is better extended and tight on the RS1. The mids to my ears are a little more recessed on the RS1, or probably more accurately, just less forward than the 225 - and thus I think sound better balanced. The highs are less piercing on imperfect recordings (and boy do I have some imperfect recordings!) which is very welcome. The soundstage is certainly wider, and instead of a wall of sound, you can pick out and isolate instruments a lot better on the RS1s.
Now, my first week on them, I was worried about my sources because my iPhone playing through a cMoy sounded, well, really awful on the RS1, which was discouraging. But after a month, they actually sound really good. Not nearly as good as my desktop rig, for sure, but I don't dislike it anymore!
But, are they worth two and a half times as much as the 225s? Maybe, maybe not. I'd pay it again in a heart beat knowing what they sound like, but I think they are just slightly overpriced. Are they as good as, say, HD800s? I think they're just as good for a lot of what I listen to.
Down the road, I might see myself selling my 225i's (and maybe my Q701s) to get a pair of PS500s. It's good to have a choice in Grados!
Disclaimer: Your mileage may vary, because my audio path is Modi->Fiio E09K or iPhone5->cMoyBB