I specifically want to be able to use Ackmate bundle, peepcode (the new 'Go to file' seems good enough) and some other custom bundles with TM2.
I tried moving the existing bundles to a location
~/Library/Application Support/TextMate/Managed/Bundles/Managed
which seem to contain all the new installed bundles, and a few other hack. But no luck yet.
I did manage to get the older themes working with TM2 though, with an approach similar to the one above.
EDIT:
I found this article on the topic.But still not able to get some older bundles to work. http://blog.macromates.com/2011/locating-bundles/