Pontos is a very stable release for me. And I like the green theme.

It installed and dist-upgraded on my Core 2 Duo desktop, a Lenovo 3000 C200 and an Acer Aspire One, ZG5. The only issue I've had is getting wireless to work on the Lenovo (so far doesn't work with Mepis either, probably a PEBKAC error). Everything else works very well.
Lately, I have been using sidux as the fastest route to testing and they do have some nice scripts. Ceni is really handy for setting up networks. h2's scripts: smxi, sgfxi, etc. are now more applicable to debian based distros though not necessarily Ubuntu. So far works very well for me with M8rc1.
sidux is a very well done and supported distro. Pontos is probably the best so far.
The liveCD is a great recovery tool as well.
So why change?
1. Just moving towards more stability; that is, less need for dist-upgrading. Priorities changing to less excitement. Also moving to where I have less connectivity, therefore choose to not have to dist-upgrade as regularly. sidux is probably the best way to run Sid.
2. The other reason was for OOo3 which due to the Lenny freeze is still in experimental. It's funny how sid gets behind with each testing freeze. Also sort of frustrating.
Mepis has always been good for me. Very stable and solid.
After Lenny is released, I will probably switch from Lenny to testing throughout menu.lst.
Currently, testing/updates is not current; and they suggest lenny/updates until further notice. I guess the desire to experiment hasn't died just more practical.