With "I'm With You", the Peppers have returned to their sound of albums like "By The Way" and to some extent "Californication" as well. And I love it. Monarchy of Roses, the opening track, wastes no time making this perfectly clear, with Kiedis' smooth-but-tormented-voice reprising its usual role, and the guitar riffs and subtle drumming are just as good as they've ever been. Brendan's Death Song is another such song, as is The Adventures of Raindance Maggie. Dance, Dance, Dance is just plain old fun to listen to.
Basically, this album can be summed up by the words "more RHCP". If you like By the Way, if you like Californication and want to relive the thrill of listening to those albums for the first time, "I'm With You" is most definitely worth it. If you've always had an intrinsic dislike for the Peppers' stuff, or of those albums weren't to your liking, you may find this new album disappointing or bad. It certainly won't change your mind. Personally, I belong to the former group, and as such I find this album to be a great effort, and I look forward to seeing them perform it live. Recommended.