It took me awhile to get used to it too...but then I just remind myself to be pleased with what I've got. Tim is a good singer, and I'm pretty sure Matt isn't coming back, so I may as well enjoy what has been chosen (unless it sucks). I still think Jon needs to let more of the musicians in on the songwriting process...if he did then there would be more variety of sound, and would over all make the band better. Not to say I think the new material sounds rehashed (to me it doesn't), but I think Jon just needs to open up a bit in the future.
I think this trilogy has been one of the strongest Jon has ever done. It's funny, even though this album was just released, I am looking forward already to another album. I've listened a lot and just want more!