Lee, what it is lacking is that fantastic hybrid viewfinder - and the larger
fantastic image file. That said, the wider angle and "faster" feeling I have of auto focus (which I need - that is the AF) and its smaller size...plus the option to change focal lengths is a big plus. The OVF is bright and clear...however it can't compare to the X100's.
Initially I bought the X10, tried it liked it but felt guilty about buying it... Well after about two weeks, I purchased one again. It is a very good camera for serious photography as well as for "snapshots"...for pictures one wants to take of family, friends, trips, etc. The X100 can be used for all these things, too...but the X10, in my opinion, offers some more options...
You ought to read through our
X10 threads, if you haven't...to read other people's opinions. Ray also has both of these and finds them both worth having. It's such an individual thing, Lee. I only have these two cameras. Do I need both? No, not really...but I do like having them both.