I go back and forth on whether to invest in another system. For me, it wouldn't be the Sony. Of the systems available right now or about to be in the next month or two, I'd either go for the EP-3 or the forthcoming X-Pro1.
The new sensor on the X-Pro1 sounds promising and I like the initial lineup of primes. However there is no mention of AF performance in the marketing, which leads me to believe it is not a strong point of the X-Pro1. So considering the AF might not be as good as some other systems and factor in the rumored price of $1700 for the body and another $500 (or $650 depending on the source) for each lens, I find it hard to justify that kind of cash outlay for another system (possibly with a mediocre AF system).
I've looked at the EP-3. The AF system seems like one of the best out there for this type of camera. I also like the available selection of primes ( I think if you're going to use mostly zooms on these cameras, you might as well stay with a DSLR since there isn't much difference in size and the DSLR performance will be much better ). But then I think about the 4/3rds sensor performance vs. an APS-C, and that holds me back too.
So for now I'm sticking with DSLR systems (and my Panasonic TS-3 - it's my "I can take it to the beach, knock it around, and not worry about it" camera for casual snapshots).
I've been looking at the Pentax DSLR system lately. One thing I like about their DSLR system is the availability of pancake primes with AF. Their 21mm f/3.2, 40mm f/2.8, and 70mm f/2.4 lenses would make a wonderful three lens kit that is as physically small/light-weight as you could probably get. If I were to be starting from scratch, I'd probably consider going this route. But then again, I like the variety of options we have available in the Canon camp. So I don't see a complete change of systems as something that will happen for me. I love the compactness of the Voigtlander 40mm I have. And it is a fine MF lens. But there are times I'd like a pancake lens with AF for the Canon system.
Bottom line: all of these systems are a compromise of one sort or another. The hard part is picking which compromise serves you best for the majority of your shooting. For me, I'm finding sticking with the Canon DSLR is the best compromise. Spending money on a second system just doesn't seem worth it. Having a point-n-shoot like a S100, GX-1 or any other where I'm not going down a path of wanting/needing additional accessories ( or lenses ) for the 2nd system just makes sense.