Pros 1. No shutter lag.
2. Quick focus
3. Zoom is great for 90% of what I need
4. Solid build
5. Has a viewfinder
6. Fast lens (in aperture)
Cons 1. Batter life on the low side
2. Twist to turn on is inconvenient
Summary I am profssional photographer, my other cameras are all Canon: 7D, 60D, T2i
At some point, having a DSLR with you all day is impractical. I bought the X20 mainly because it has no shutter lag. The camera just doesn't disappoint; it focuses fast, has no lag, great quality lens, shoots in almost dark and the image stabilization works well. It is a joy. A friend of mine bought the X100 but I can't see having to limit myself to one focal length, I am the anti-prime I guess. I've taken the camera on the streets, to concerts, events... you name it, the camera performs. I strongly recommend it.