What did you think of Mahoromantic? I'm still going through Gainax shows and I wasn't sure whether or not to hit that one up. I had no idea it was directed by Hiroyuki Yamaga.
Mahoromatic is okay. The serious parts are mostly pretty good, while the comedic parts are hit or miss. It does have lots of fanservice of course, particularly in the comedy/harem episodes, but the show has a serious side, and the plot there is solid and kept me watching to the end. It's also got a completely crazy, Gainax-level final episode... good stuff! Oh, and the first season's OP and ED are really good. S2's are good as well, but not quite as great as the first season's are.
Oh, the followup series, that 2-episode OVA from several years later... it's all comedy, and isn't very good. Watch the two original seasons, but that is optional.
The OP of S1 fits great with the serious side of the show, and still is quite good...
http://www.youtube.com/watch?v=ZIDz2uwqHsM
And the ED fits great with the comedic side. Though it's probably actually sillier than some of the actual episodes, still, it fits well.
http://www.youtube.com/watch?v=UQc6_bnXcWI