The Verge has the full story on how a startup built the Gmail app Google couldn’t, or hit the announcement where I saw it on 9-5 Mac.
Personally I think it looks great and has some nice things beyond what you get in the default client (ie: faces associated with addressbook entries, a built in photo browser), but I don’t do enough emailing from my phone for the $2.99 to be worth it (and I don’t use gmail for my primary mail). Still, if you’re a heavy iOS gmail user, or love the desktop client, this might be the app for you!