I have my X10 since three weeks. I am really enjoying mine, never had a camera like this (and I have quite a lot of cameras!).
It is perfect and really well planned for me, something brilliant like Olympus XA or OM, it could has been designed by Maitani. It contains the archetipal of all the rangefinders camera for me. It is little, black, with a viewfinder, the on-off switch is something that recall both the lock of Contax than the collapsible lens of Leica, and the wheel on the top also are positioned to recall both the Leica II than the over-underexposure selector of the OM2. Reeeally silent in the stealth mode (if you press the noise off button), more than any other camera I ever had! Just this would woth buying.
I do not have the X100, I suppose it is a great tool, but this is black and has a zoom lens, with focal expressed in 35mm equivalens, so it is a great, totally different camera from the X100. I do not mind it is not an X100, I would buy an X10 anyway.
It is a great rangefinder-alike camera at a very low price for its capabilities, and I think that it can do something that most of the other cameras can not do (except maybe the little XA): to shoot in a totally invisible quite silent way.
The EXR mode is something that any camera should have. If you wish, you can select any of the function of the camera going through the menus, but when you are doing street photography and you need a fast, intelligent choice taking the best from the small sensor you can select EXR and just mind about framing. It is something that any camera should have, like autofocus (I do not think it is essential, I love to shot without exposure meter and autofocus, but those option are good on a modern camera).
I am a GREAT X10 fan!! 🙂