You might say I have a long distro history so I'll add my 1.7 cents (it was 2 cents before the recession).

 
Loved Mandrake until it got buggy. 
Mandriva came from Mandrake but never recaptured the glory.
  1. Both had very easy to use but powerful administration tools. 
  2. Wonderful menu structure
  3. Looked good
  4. Excellent hardware discovery. It could load the drivers for your blender if you could plug it in.
  5. Package management from the Gods when mortal man was painting on cave walls.
Why I stopped using them
  1. unstable repositories. Software was constantly broken. 
 
CentOS for servers - it's just the most stable feature rich distro for servers (from the commandline). 
 
SuSe for servers if you insist on using a GUI to manage it. Has the best GUI Server admin tools.
 
Ubuntu 8.04 - 10.10
  1. Tons of software packages
  2. Gnome2 became usable for bipedal primates with large frontal lobes.
  3. Install process so easy a baby stuck in a mineshaft could do it. 
  4. Everything just works and when it stops shaking a rubber chicken seems to help. If it doesn't work on Ubuntu it probably doesn't work on anything that runs Linux including orbiting brain lasers and fembots with a penchant for evil.
Why I'm looking for a replacement
  1. Software packages broken.... sounds familiar.
  2. Got tired of looking at desktop color themes best reserved for a 1970s kitchen with accompanying man cave with wall to wall shag carpet.
  3. Moved to the Unity desktop which is targeted at a branch of hominids possessing much smaller brain functionality that have been extinct for roughly 4 million years. Possibly as a result of a poor market study with limited subject availability to question and those who they could dig up didn't have much to say.
  4. Including the word Ubuntu in my online dating profile has not improved love matches. In addition translating the original Swahili meaning to English only leaves me looking a bit creepy.
  5. Ubuntu sounds like something my kids used to say when they were a year old and needed changed. Looks like it too.
 
Distributions I'm interested in but haven't made a decision about
 
Linux Mint DE
  1. Based on Debian so the software packages may actually work
  2. Uses the XFCE desktop so any sane human should feel comfortable with it.
Possible downfalls:
  1. A bit rough
  2. A bit ugly
  3. Linux Mint DE with a port scanner vs. Clint Eastwood with a Bowie knife would be a good fight.
  4. Having the same name as another distribution that has broken packages gives me the shivers.
 
Mageia

  1. So far every single package in the repository works. Ex Mandrake developers who must have learned their lesson.
  2. Doesn't talk to me like I'm a baby   

Possible downfalls:
  1. Only two packages in the repository.
  2. Just when I learned to pronounce Ubuntu this comes along.

 
The nice thing about Linux is you can try them all for zero dollars. I think a good practice though is to have a shared network drive where you put all of your stuff so if you choose to wipe out your machine you don't lose anything. Actually this is a good practice on any OS.