It seems to me that werewolves were included more for a beginning character than for higher levels. I'm at level 40ish and I have no use for the beast form power. You can't access your inventory, spells etc and it doesn't really outmatch my regular character. It certainly isn't the gift that the other wolves claim it is. It's reasonably well implemented, but it seems like it was more useful in Bloodmoon than Skyrim.
Can you become a vampire while you have the beast form power (not at the same time but could you do both?) I've fought several vampires and not caught the vampire disease.

You become 100% immune to disease as a werewolf, and as for not being useful, I find it useful just for the 1400 carry weight you get while transformed, as well as being able to run faster than a horse.