Debian Testing is good. Seemed to work OK for the 30 seconds I ran on it between upgrading from Lenny and upgrading to Sid after two different fresh installs. (Seriously though, I have used it extensively and it's a great distro. I was just impatient to get Xinput 2 as soon as possible.)
These days, I use Debian Unstable with the Experimental repositories enabled, because that's... how I roll. (Ba-dum Tish!)
Or you can try Sidux, it's a stabilized rolling release based on (and kept mostly in sync with) Debian Unstable. Haven't tried it myself, so I can't really recommend it. But that might be what works for you.