I love my druid tank, he's proven to be just as capable as a pally.
About the only thing I miss is the Avenger's shield for caster pulls (got to love that silence),
but I either move the fight to the caster, or use line of sight to pull the caster to me.

At the moment I hold aggro with just swipe spam and the odd maul, but I'm working towards a macro that should up the dps/tps.

The druid has talents that make you crit immune at 80 so I felt the gearing up process wasn't as painful as the pally.
(this was pre ToC so running that on normal is apparently a good way of gearing up quickly).

Buff wise the pally wins.

The druid also has some nice abilities to help out when damage is high - Barkskin (use this alot on multi mob pulls), survival instincts and frenzied regen can help tide you over if somethings taken your healer out for a few seconds.

Definitely give it a go.