To my ears -- and based on the many IEMs I've heard so far (but I haven't heard any of Ultimate Ears' universal-fits yet) -- I think the UM2 is maybe the best value (given its high performance at its typical street price) of any of the IEMs I've tried. I first heard it at the National Meet, and now I have my own UM2 (and have used it quite a lot since).
First of all, the UM2 sounds fantastic. And though, in my opinion, it falls short of the upcoming SHURE E500 in terms of overall performance (the SHURE E500 being the best universal-fit IEM I've heard so far), it still plays in the same league in many respects; and, depending on where the E500 shakes out in terms of street price when it's released, the UM2 will likely be significantly less expensive.
Secondly, I find the UM2 easy to insert (second only to a custom-fit in terms of ease of insertion), and among the most comfortable IEMs to wear, thanks at least in part to the über-flexible, barely-there cable it uses.
I haven't heard the UM1, so I can't comment on it, but the UM2 has a performance/price ratio that's hard to top.