Debian's Sid repo is the place to find the latest, greatest and sometimes buggiest software. Alpha, Beta and anything after, is held in Sid until it is tested extensively and found not to break very often.
From there it travels to testing, where it lives until the Debian maintainers are satisfied about its stability and its security. Only then does it progress to the stable repository. But that journey can take a couple of years. In the meantime, if you run stable, you live with what feels like 'stale' software. Sure its rock solid and err... old.
If you want more up-to-date software options, you can go 'Testing', where things don't break that often, or if you want to live on the edge, you can go 'Sid', where things don't break that often. Was that an echo?
No. Its right. 'Sid' may have a reputation for buggy and untried post-alpha software, but that reputation is not wholly accurate. A lot of software in 'Sid' is stable and secure.
If you want to try 'Sid', take a look at 'Aptosid', a distro based on the Debian Sid repository. It doesn't bother with stable or testing. Go straight to Sid, if you pass go, collect $200.
Aptosid is a full-blown distro running KDE 4. Its lean, fast with the latest software. Aptosid comes as a LiveCD, so you can try before you buy.
I've been running Aptosid for a while now, and nothing has broken yet. Its usable, solid, light, fast and fun. What more could ya want?
If you want to try the Debian OS, but want an easy path into the Swirl, go download Aptosid and give it a shot.
You might like it.