On my Cygwin environment on Win XP, Vim 7 appears to run fine with one exception: the vimspell.vim plugin. It apepars that Vimspell conflicts with the new built-in spell check functionality in Vim 7. The symptom of this is that one starts to type and a massive amount of doubled or missed letters start to appear (and, no, I was not drunk when I noticed this). Removing the vimspell.vim plugin works fine.
However, I like to use a consistent ~/.vim directory across all my shells, so that I can store it in CVS and enjoy the same settings on every system. To do this across a heterogeneous environment of Vim 6 and Vim 7 boxen, I have made the following change to vimspell.vim:
61c61 < if exists("loaded_vimspell") || &compatible --- > if exists("loaded_vimspell") || &compatible || v:version >= 700
This will short-circuit out of vimspell before it gets loading if the version is Vim 7.0 or above.