Yes and yes. This was a big reason I wanted one. (Unfortunately I haven't been able to bring it to a game yet as my gaming group has been having scheduling issues)
I also recommend the App "Power Attack XL" its a quick reference for all the D20 rules. Super handy when you need to look up a spell effect quickly without opening Good Reader and finding the appropriate bookmark!
I use it for this, and there's also HeroRef for you HERO-system players out there. Oh, and Dicenomicon, though that's a bit pricey. There's talk of porting Maptool to the iPad, which would be all kinds of awesome.
If you're playing D&D 4e, iplay4e.com has an awesome web based character sheet. It uses the character files from the official character creator program and, if you have an active D&D insider account, will also show the rules text for your powers and feets in the character sheet.
lvl99games (lvl99games.com) is already working on an app similar to maptool. I use their DM Toolkit already.