I've been catching up on continuations from last season.

Ultimate Otaku Teacher: This one really surprised me when I first watched it in the Spring lineup. It wasn't super amazing, but it was good. Definitely worth watching. I took a break after episode 12 to focus on Summer anime a bit though. I finally watched from episode 13 - 21 yesterday, and it has kind of declined. The new characters aren't as interesting, the new opening and ending aren't as good, and I feel like it's going to end on a really weak note. I'll still watch the last few episodes of the season to see if they have some good arc to finish things off with, but my hopes are a little low. It hasn't gotten bad, but it isn't quite the show that I was enjoying either.

The Heroic Legend of Arslan: I'm actually still catching up and am on episode 17, but this one has stayed decent. Things have slowed down a bit, but there's still a lot of battling and drama. I have no idea if the show is progressing in a way that we'll get a satisfying conclusion after only 25 episodes, but I look forward to see more of what's coming next.

In terms of this season-

I recently caught up on God Eater as stated previously, and watched the latest episode the other day. Alisa's boobs make it a solid 7.9/10. I would like the show more if it didn't seem to be airing less than basically any other show I've watched this season. I mean, the latest is episode 7 while other series are airing episode 10. I know it started late, but having to skip it on some weeks on top of that is brutal. Overall though, I'm appreciating that this isn't a black and white, monsters bad, humans good situation. It's actually a complex problem that makes for an interesting watch.

So One Punch Man seems so insane thats its gonna be the most awesome anime of the year... it just oozes awesomeness

I'm bummed out how the God Eater adaption turned out ... 

Since it's 1 cour I didn't even expect them to cover Lindow's Return Arc but at this rate I doubt they'll be able to introduce Shio ... 

They'll have only covered the first 5 or maybe 10 hours of the game if I'm been generous ... 

I liked the Lucky Star and Seitokai Yakuindomo OVAs.

I liked the Darker than Black OVAs. They explained some major events that happened in between Season 1 and 2, and make it a little more clear why one character was gone, and why another was so messed up in season 2. Looking back, I'd honestly recommend watching those OVAs as if they were regular anime episodes, they were such high quality.

Can't think of many other examples...usually it's just fanservice, which means you'll love or hate them depending on how much you liked the series. I think One Piece has good animated adaptations of the omakes and even the one-shot, but I haven't seen much of the anime for that.

It's impossible to toss all OVAs under one umbrella, as the usage for the term of OVA is pretty broad. Sometimes OVA means just extra scenarios that couldn't make it into the anime, like the Angel Beats OVAs. Other times a series may get totally remade in a non-standard fashion and gains the title of an OVA series (such as what happened with Hellsing). Sometimes OVAs will simply be used as a continuation if an actual new season wasn't approved, like what is still happening with the ever slow releases of Kenichi: The Mightiest Disciple, or what happened with Tsusbasa Reservoir Chronicles (both examples where OVAs do the series justice).

Are there good OVAs? Tons. The biggest problem with the most standard way you see OVAs is that anime sites and the like won't place an OVA chronologically in the anime timeline. Many OVA episodes, as I mentioned, are scenarios that don't make it into the anime. It seems a lot of the time, that doesn't just mean content that happened after an adaptation ended prematurely. That may just be a scenario that happened say, between episodes 4 and 5. It loses a lot of impact if we finish a series though and then see these OVAs that don't have nearly the same impact as the ending of the show.

Basically, when you know a series has OVA episodes, verify where they fall in the timeline first. For most anime, somebody, somewhere, will have compiled a list of what episodes fall where. They should be more enjoyable if you watch them when the events are at their peak relevance.

Those OVAs should have been released before Season 2. I couldnt understand anything when i started watching Gemini of the Meteor.

Yeah really. I was watching with a friend who had seen it previously, so I had the benefit of knowing I just didn't miss something....but it still confused the heck out of me. I guess they wanted to make it a mystery why Hei went from being Batman to a child-beating alcoholic.

On that note...I wish Bones would animate the manga arc. They could easily get a 12-episode season out of that.

There was a time when OVAs were often high quality projects.  The Cutey Honey OAVs come to mind, or the Blue Sonnet OVAs.  Some of the Ranma 1/2 OVAs were excellent.  Top wo Nerae 2! Diebuster (Gunbuster 2) was bloody fantastic.  It blew me away when I first watched it.  Many of these were works intended to sell on their own, as opposed to a lot of the DVD extra content that pops up now.

I really enjoyed the Bungaku Shoujo (Book Girl) OVAs, too.  They felt different and mysterious.

One of the most awesome OVAs that almost no one has ever seen is Denpa teki na Kanojo.  I loved it to death and wish there were more.  The female lead is so interesting because you're not quite sure if she's dangerously insane or not.  Psychological suspense anime done right.  Seriously, look it up, anilinkz has it, and it's only two OVAs.

(Don't watch more than half of this AMV if you want to watch the OVAs because of spoilers)

Oh, and the Yozakura Quartet OVAs were incredible.  I know the series is complicated but it's just so damn good.

And, of course, this bit of absolute brilliance.  Some people you do not piss off.

That arc is after the events of season 2 or just a side story? Because if it's a sequel i'll start reading it right now!