There's an interview somewhere where he was asked about the show before he was hired for E15. He said he's never bothered with it and never seen it and was very dismissive. Now that he works for them that may change. Of course there won't be any more work will there?
David H has tweeted David B and has been vaguely positive about SGU since he signed on to appear in it. I don't think he likes burning bridges (so to speak, LOL) and has had some ongoing back and forths with DB. Although you never know what he really thinks, I read something online years ago from a person who knows him and he had less than positive things to say about TPTB. He can't afford to alienate the people who may be hiring him for his next project. And he has always been one of the producers and writers favorites, so I don't think he's going to be incredibly upset with them in public, they made him the de facto lead in SGA, for one thing.
Also, his sister, Kate, is attending a class or workshop with John Lenic, one of SGU's producers and has been tweeting her SGU fanishness quite a bit lately.
I will admit, I am not happy with David appearing on SGU and kind of feel betrayed by it because I am a big fan of his, but then again, I don't have to pay his bills.
ETA: E15 is Episode 15, Seizure, I believe, where David H and Robert Picardo will appear.