Well, I'm one of those guys who love stories. You know, the thing that we don't really find in 3/4 of anything. And so, HDxD have a pretty decent story, it's a light novel after all, story is important. Writing skill too.
It's kind of sad thinking that the anime is pretty much a pair of tits. Pretty strong to put fanservice where there no need. Even better to do an ending and opening who is fanservice. And, hell, the anime is fanservice itself. That's big.
What ? You want something worth watching for ? Well, HDxD can be a very enjoyable material if you use it for sexual enjoyment, I think. It's nearly uncensored for a good reason.
But if it's story that you want, go for the light novel or the manga. The anime will just put your mind upside down and made you wonder what the hell you are doing with your life. It could destroy your self-esteem. Seriously.