My own personal advice is get a non-G version. Either buy brand new AP set or buy 2nd hand local non-G set.
You cannot change the hardware la bro. The CPU and GPU different between this two version. If you flash a G  version firmware updates on a non-G phone then you'll end up soft bricking that phone already. So there's no way dealer/seller gonna sell a G version phone as a non-G one. It's IMPOSIBBRUUU..!!!
~~haha

Nothing MAJOR exactly. Well known issue was its camera prone to freeze. And a few issue with sdcard.
Other than that the phone is okay if you gonna use it as it is.
But if you kaki flashing then you're in deep problem as the G version got very limited custom roms and kernel to ply with.

That's it, I let go my SGS2 already. Going Galaxy Nexus I think.