its "casual" fan service though and, by today's standardm not a "ton" if you ask me, but yeah its there - more often than not, but they way its done most of the time you'll end up thinking "wow, that girl looks good" rather than "get that ass out of my way, its embarassing"
I've already fallen for that mage-chick

and for the show which aired 2009
I havn't seen it either, but from the looks of it, if i compare the art - the old one loses horribly (the OVA is really good though) but thats only natural, since its ~5 years older.

the OVAs fill certain gaps between the episodes
the timeline is something like Ep1-4 -> OVA1+2 -> Ep 5-10 -> OVA 3 -> Ep11-13.
but I'm not sure because I didn't watch them so far