I think they're definately the most popular. They have a great reputation.
I have read a few complaints from people on here about them. Mostly noises and things of that nature. Can't remember reading anything negative about their performance.
There are definately a few other brands of coilovers that I'd look at.
I'm telling you you need to search and read through all the reviews before you do this...
In the process of restoring an 07 335i