Agree about the 'lefty' comments, though she still does this quite well.
My beef with her serve is its inconsistency. She just can't seem to let if flow on automatic pilot like she used to. It wavers a little too much, and on the days it does, her confidence dips a little (as with anyone). When her first serve percentage is high - even if the speed isn't really high - she's on pretty solid ground, as most players don't seem able to hurt her when returning her first serves.
I know it sounds logical that returning any player's first serve should be more difficult, but the top players these days don't seem to be troubled by most players' first serves. Only Serena, Venus, Jennifer, Monica, and (occasionally) Amelie seem to really cause problems against the very top players when their first serves are going in. Once Lindsay's back to 100%, she's in that group too.
It doesn't seem that the first serves of Clijsters, Henin, and Hantuchova are quite in the same league yet (though they likely will be with a little more time).
All in all, though, I think Monica's serving much better this year than she has in the last couple of years (with the exception of the Henin match at Wimbledon