As a big fan of the original British version I didn't even bother to watch the US version. I gave in a couple of days ago and am now up to date and wow is it good. It's much, much better than I thought it would be.
Much like Life on Mars, the UK and US versions are different enough and both good enough that I find it hard to pick one as my favorite. The tone of the US Being Human is definitely lighter, despite being just as full of nastiness.
Both are very good!