hey, yea i actually just got my UM1s yesterday...and they are fantastic. I think they are significantly better than the sennheiser and creatives, which both sound very similar, so similar that I'd go the creatives for sure. In this case, I think its worth spending 100 rather than 26-50 if you're looking for really good sound. The creatives/senns to me serve a great market for those who just want cheap semi isolators to throw around or don't notice/care for the difference in sound quality.
One of the biggest difference between those 2 and the UM1s is that the UM1s are just much more balanced, this is especially noticeable in the midrange, which is the most crucial area in sound frequencies. The UM1s and other 100+ iems just have a smooth, natural, correctly balanced midrange that sounds 'real' where the other cheaper iems, like the sonys, creatives, senns, etc have midrange that is usually not enough (which I definitely notice with the senns/creatives) or not balanced. The result is like hearing as if the singer is singing backstage whereas the more expensive iems sound like you're there in the studio or concert with them. Detail is also much easier to hear, you can hear teh differences between songs/recordings, and the nuances of instruments/effects. Great recordings sound absolutely great with these UM1s whereas the creatives/senns will sound just a little better than worse recordings.
The other big difference is bass...the creatives/sennheisers have much more bass, I think its bloated bass, not overly boomy, but not very well balanced imo, which results in overpowered mids but some people like this sound.
Also, with the triflanges, the isolation is much much more than the creatives/senns. I can barely hear people scream without any music playing, since the triflanges go in so much deeper than the short silicon tips with the creatives/senns. Now i'm not sure if you can put triflanges/biflanges on the creatives, but I dont think so.
Oh and comfort wise, these are fantastic too, just as comfortable to me as the creatives/senns. The drivers are very light and so is the chord and they fit flush with your ears that people can't see anything from the front.
Microphonics from the cord are also much less noticeable than the creatives/senns, maybe its the braided cord design and material, but I like it.
So, I think it was way worth my money, I so much more happy with these than my creatives/senns. BUt the creatives are a great deal for 26-30, for the less discerning listener. They definitely serve their purpose well, just don't expect them to sound like 100+ iems.
My advice would be to splurge a little for either the UM1s, er6i, superfi3, or shure e2/3, the e4cs and such are probably out of your price range. I've bought so many cheap earbuds/headphones and have never been satisfied with their sound, you get what you pay for in my opinion with iems. I think 100 bucks is the sweet spot in terms of value/performance, I wasn't willing to pay the extra $190 for the UM2s better sound.