I just received my new Westone 4Rs.
1. They seem more solid than the UE900s.
2. They fit better than the UE 900s. I was able to twist the memory plastic, and it maintained the shape. This was one of the most annoying things about the UE900s. I was constantly fiddling with the memory plastic, trying to get it to stay behind my ears. Putting the UE900s in my ears was a chore. The Westones went in with a perfect fit in seconds.
3. I love the sound. I'm no audiophile, so the subtle differences are a bit out of my league. But the sound is in the same league as the UE900s, and that is good enough for me.
4. I prefer the Westone foam eartips to the Comply eartips I had for my UE900s. Not sure how they will hold up over time, but the Complys would fall apart after about 3 weeks. Even if these do the same, these are cheaper. I will also try to make my own from ear stopples, which I used to do with my beloved Triplefis, but couldn't really do with the UE900s, because they would not stay on for some reason.
5. Thank the heavens for the old-school cable connectors! I loved this connector on my Triplefis, and as mentioned above, I suspect all the audio cutout problems in the UE900s (and the various Shures) are because of that worthless new connector.
The only negative I see is that it doesn't have a control mechanism for my iPod, but I can live without that.
I swore off Shure forever after they refused to honor their lifetime warranty on the SE500s (long story). I won't swear off UE/Logitech for the UE900 sin, as they also gave me my much-mourned lost Triplefis, but I will wait to see reviews and experiences before buying another of their products in the future. The way they've handled the UE900 fiasco does not warm my cockles, despite their excellent customer service.