Yesterday, I made my triumphant return to CrunchBang!
I have been running a Debian LXDE testing/unstable system on my Dell Mini 9 for the past couple of months. But with the official release of #! 9.04, I decided to give #! another try.
The verdict? Debian does indeed seem a little "peppier" (though I have just installed the 2.6.30 kernel in #!, maybe that will help) but it is not a huge difference. I definitely agree that the default Debian Gnome desktop is a lot faster than the default Ubuntu Gnome desktop, but I think when you just have Openbox and a few apps, the differences between Ubuntu/Debian/Arch/Whatever are minor. #! doesn't use a lot of resource-hogging applications, so I think it would be pretty fast no matter which distro it is based on.
The most compelling argument for keeping #! based on Ubuntu is hardware support. #! 9.04 runs flawlessly on the Mini 9; Debian required some "tweaking" to get the wireless working. I would guess that a huge part of #!'s success is due to Ubuntu and its awesome hardware support. I think if #! ever does switch over to Debian, we will see a huge increase in newbie questions like "why won't my wireless connect?" "where's Firefox?" etc. And from what I've seen of the Debian forums, they are not supportive of "remix" distros like the Ubuntu forums. (Let's face it, positive reviews on ubuntuforums.org are a big part of #!'s success.)
In conclusion I personally would love to see #! Debian, if for no other reason than rolling release. But I think for the growth and future popularity of the distro, Ubuntu is the correct choice.