I'm currently taking a look at the Teenage Engineering OP-1 synth -we've got one in for review and I am having a lot of fun with it. The instrument is surprisingly deep and flexible and pretty compelling - are my first thoughts. I also introduced it on this week's Sonic TALK podcast (229) - there's a video of the show here.
As ever, please hit me with any questions you want answered in the review via comments below or via Twitter @sonicnick.
While researching, I came across the unofficial OP-1 Forums : ohpeewon.com - worth a look for those either trying to get tips and trick on usage or research whether to buy one.
In fact, just posted there this very morning was news of a project made with the OP-1 by forum user Molotov under the name Duke Slammer.
So since buying my OP-1 (first post-beta batch) I've been posting up tunes here and there in this fine forum. I have found the OP-1 such an really inspiring box to work with, so much so I decided to make up a new project based solely around using the OP-1 as the main sequencer/recorder, replacing Ableton in this instance.