I don't view it as a replacement or a Dslr, even though it's going to be. It seems to be better at some things and worse at others.
For news and sports nothing will touch an SLR for capturing fleeting dynamic moments, but for portraits, social photography, travel stuff, in other words all the things I tend to do, I think the Fuji is going to do a better job. Image quality is very important for me and the Fuji seems to match the resolution of full frame DSLRs while giving the quality of colour rendition and pleasing look of a Leica. That's no mean feat. Add very clever on-the-fly dynamic range adjustment and superb in-camera Jpeg conversion and a lot of the perceived negatives disappear.
The focusing, at least with the 35 1.4 is absolutely fine (I think the latest firmware has improved things since early review samples). This is, however, an issue for me and I wish it would focus like a D4, but you can't have everything.
The big plus is it's a lot smaller than a D300 and 17-55, which is impracticably big either on a bike or when carrying ten tons of baby crap around. The old adage that the best camera is the one you have with you comes into play for me.
The one real downside is a 300-ish shot battery life, so the one I just ordered will come with a spare battery..