LastPass has always been available on iOS via a couple of bookmarklets, but that sure isn't the same than the constant-autofill experience you get on the desktop. Since mobile Safari doesn't allow for any sort of plug-ins, LastPass opted to create an entirely new browser, so you could speed through the login process without any sort of workarounds. The iPhone app requires the (remarkably cheap) $US12/year premium subscription, but the iPad app is free for all users.
Apart from LastPass integration, these browsers don't have a ton of other features. The iPad browser does have tabs (which is awesome), and while it doesn't quite measure up to previously mentioned Perfect Browser, having that integration is awesome when I'm jumping between apps like Facebook, Gmail and other web apps. There are definitely a few bugs in the password manager portion of the app, but if you can get past that — which I personally can, since I really just want it to input all my passwords for me — it's a pretty handy app to have around, especially if you're not looking for a super-advanced browser.
LastPass and LastPass Tab are free downloads for iPhone and iPad, respectively. The iPhone app requires LastPass' premium subscription, while the iPad app is completely free.