Well, I'll assume you've watched season one if you're looking at the Seitokai Yakuindomo OVAs. Honestly, even though 8 ovas is a lot, as a whole or even stand alone these were pretty much just as good as the original series. The story didn't change, obviously. You'll get more of the same type of sexual comedy that you should be used to now. Don't be expecting character changes, new opening and ending themes, newer animation style, etc. Basically everything, is the same old stuff you must have liked from season if you're looking at this.
I do have two reasons for why I don't think the ovas and season 1 are equally as good. The first being that the one reoccurring segment kind of gets old fast and it's not nearly as funny as the other jokes. The second being that the animation and art quality seemed to drop a little in the last episode or two. A lot of scenes seemed to be really grainy compared to scenes from previous episodes. These are the only complaints I have.
If you liked season 1, check this out. I think you'll enjoy it like I did.
