I rented a x100 before I got the x10. In terms of IQ OOC, the x100 is a clear winner, because of the sensor size, the IQ comes very close to the midrange Canon 60D that I own.
But I didn't buy x100 in the end primarily because there's no zoom. I know the 23mm or sth focal length is ideal for street photography, but I just felt somewhat handicap by the fixed length. And also, it's too expensive in my opinion.
When the x10 was announced I knew at once it was a camera I wld get as my secondary "compact" camera. In terms of size it definitely is more portable than lugging my 60D ard.
During the first week of mainly using the "dummy-proof" EXR mode, I was blown away by the intelligence of it. Pictures taken under several conditions just appear sharp and with great color tones. I was fast convinced that I can use the x10 to just dont think so much and shoot. Take all the manipulative aspects away, and I find myself focusing more on compositing a great frame. It is just a joy to shoot with this small cam.
In all, I wld say that the x10 is a very good complement to any dslr you may own, for serious enthusiasts. For ppl who are starting out in photography, it is a great cam to start with, but what photography techniques you can master out of it, might be lesser than what a dslr can offer you.