Lazy afternoon spent porting git-anenx to build under ghc 7.10. Required rather a lot of changes to build, and even more to build cleanly after the AMP transition.
Unfortunately, ghc 7.10 has started warning about every line that uses tab for indentation. I had to add additional cruft to turn those warnings off everywhere, and cannot say I'm happy about this at all.
I'd be interested to hear your reasons for preferring tabs over spaces, if it's anything more than an aesthetic preference.
The GHC trac suggests that it was turned on by default because beginners accidentally mix tabs and spaces and get very confused.