I fucking love OVAs. All hentai is OVA, it is the perfect format for anime too. Sure you have to buy it (not in our case) but the OVA allows you do do nearly anything you want without the risk of censorship (except for blurred genitals) because it was broadcast or shown on the big screen. They can as short as you want, like 15 minutes, or on the order of epic length like Legend of the Galactic Heroes. You can realize them whenever it's beneficial to you, and you can spend more time and money on every episode rather than cutting corners to satisfy a deadline. This is also why OVAs are perfect for longer series, no need for filler, and no reason to add it, no one would buy it.
More anime should be done in the OVA format, as it can probably give us the best adaptation in the animated version.