Yeah, the grooves and the metal grates on the bridge- kinda feel the same to me..  I just try to finess my way through it- just focus on being smooth and let the bike do it's thing.  
No, those uneven pavement joints someone else brought up here earlier- those scare the crap outta me!  They run the direction of traffic, and sometimes meander across a lane instead of just between two lanes..  This things suck bigtime.  I usually try to cut a little wide, and then cross over at a more acute angle if possible.  This is not always possible in heavy but fast moving traffic.
Jason