I'm running several 32-bit apps on my 64-bit Ubuntu system (also 9.10), and it wasn't terribly painful. You might need the 32-bit libraries (I needed ia32-libs and util-linux, I believe), and you might have some configuration to do, but I've at least found it do-able. I've not compiled 32-bit applications on my system; I suspect it would be a bit more difficult.
Since Ubuntu's built on Debian, this article might give you a little more insight.
Just for context, I'm running FlexBuilder Alpha, Firefox, Eclipse, and a Flex & Java SDK all in 32-bit without any problems.
If you have very specific applications you need, have you considered running in a VM? I absolutely love VirtualBox, and it might save you some unnecessary headaches.