Well, I started with slackware (well, actually SuSE when it was still a rebranded slackware, around linux 1.0.8ish), and I don't really want to dive into deep ends for my work machines anymore, I just want them to work and be moderately up to date. Ubuntu looked so promising at 7.04...
I use 10.04 LTS on work machines (by which I mean, machines at my workplace) simply because things stay the same on it and I'm not going to get calls saying "this huge colourful bar has appeared on the left of my screen, what on earth is it, and furthermore where on earth is my Thunderbird menu bar?". We have a lot of older users who are not especially computer-literate, so an interface that doesn't change is valuable to us.
The machines are also fairly ageing, and don't support the composited desktop. I did test Ubuntu 11.10 beta on one, but it was so slow (with what I assume was Unity 2D) that it would be unusable for day-to-day work. All we use at work are Chrome, Thunderbird, OpenOffice and Audacity - why would we need Unity? Why can't we turn it off?
For me, Ubuntu definitely peaked at 10.04 and I'm going to be looking elsewhere in the near future.
Isn't CentOS more designed for servers? I'm not sure. I've considered Debian Squeeze, but it's one of those things I've never got round to looking at in enough depth.
Our older users are in their 60s and 70s. We're a non profit radio station and several of our volunteers have never used a computer before, or have had only a passing involvement with them.
CentOS claims to be a clone of RHEL. There is a desktop install package that puts Gnome with the usual (firefox, openoffice, evolution). There would be some post installation fiddling with different repositories to get any sound software you need working. Scientific Linux is another distribution based on RHEL but which changes the binary packages more. Again, repositories and some twiddling.
What sound software do you use? Does it involve Jack?