Oops, a month to reply... Sorry.
Anyway, I find the re0 soundstage smaller than the ie8's, but each instrument is more clearly defined with air between them, unlike the ie8's where the sounds from every instrument I feel wash over each other a bit. To give a quick overview of my impression of the re0:
When I listened to them for the first time the very first thing I thought was; "crap, that's sharp", though half a song in I had already adjusted - and then for the next few days every time I started listening to them it took a few seconds to adjust, though I quickly never felt that any more, even when switching directly from the ie8 to the re0.
In general I prefer the re0's sound wise to the ie8's, they really do have a lot of detail the ie8's lack, and the lack of bass some people complain about I don't notice in most circumstances. The bass sounds different, though in several songs I would actually called it more refined... it's not perfect though, for example I remember listening to 'rock it' by subsenix for the first time with the re0's, a very bass heavy track, and thinking the bass was sounding great until I switched mid-song to my ie8's and the instant improvement was night and day. I also find the re0's aren't always the best at sustain on low notes such as those from bass guitars, making the odd song sound completely different and I believe _less_ accurate than through the ie8's. The first time I noticed this was when listening to alice in chains unplugged album, I forget which song off hand, but I remember A-B'ing mid song - it really sounded like a different track through the two iem's.
Unfortunately since getting the re0's, while I love the sound, I haven't gotten too much use out of them for one simple reason; the microphonics are appalling. The re0's I also find draw a lot more attention to the music than the ie8's, which as I believe you said, maybe isn't always desired if you just want music in the background while concentrating on something else such as reading - with the ie8's the music just flows by in the background, with the re0's I can't help but pay attention to it - this is of course in no way a bad thing, if anything I would say it's a good thing, although for this very reason there are some situations I would rather listen to the ie8's.