I like that they redesigned the baddies. It adds new flavour to the games and doesn't make it literally the same game but prettier. All gyms have new puzzles, just like HGSS, so that's a plus too. Basically, everything changed from RSE is a plus in my book, since it gives the old players something new and refreshing, while still having the RSE feel. That's what made me somewhat like HGSS, while I hated every moment of FRLG.
Another thing I'm happy about is that Pokemon don't follow you around. I always found it useless in HGSS as my ace is always the sixth Pokemon, while the first one is something weak I'm training. Sorry, but the feature is useless if something random is following me. Plus I'm spending most of the time on a bike anyway.