I recommend you go to
www.distrowatch.com its a great site for EXACTLY the question you just asked....
Go on the mandrake page and there's a really neat comparison going waaay back on all the package versions so you can quickly see what you are missing and if you feel you need it.
As for "keeping up" well that depends, if you're running an net accessible server, by all means you should keep up AT LEAST with the security updates...but otherwise, its up to basically whether it works for you ...
