Speaking of recent games:
In terms of surprise, I would have to go with TNA. Layout looks simple and no ramps, undersized cabinet compared to other games. Wasn't expecting too much but dropped in a few coins and was blown away. The minute the music started it felt like the machine was alive - the shaker set to the soundtrack was awesome. Its a fast, brutal pin but I managed to start the reactor and it was AWESOME. Really hope to get it in my collection one day. Scott did an awesome Job on TNA!
In terms of letdown, I would probably go with The Beatles. I heard a lot of hype surrounding this game and finally had a chance to play one but didn't enjoy the flow. It felt like an old EM with a few modern toys on the playfield. It felt like more of a Beatles fan collector piece than a players pinball machine. I kept waiting for it to progress but it just didn't happen for me.