DSLRs are versatile. That's their major asset. They can do everything well.
Until recently, mirrorless cameras either could not offer the image quality of a DSLR, or could not do so at a comparable price as a DSLR. That has changed. My X-Pro1 easily outshines my 5D Mark II in terms of sheer image quality. The XF 35 f/1.4 is far sharper than my 35L ever was (though the new Sigma 35 appears to be a winner), and is far smaller, to boot.
That's not to say that I pick the X-Pro1 for every situation. For macro, the XF 60 only does 1:2. For lenses >135mm (FF equiv), the EVF is far too unstable. But in that 21-90mm range, the X-Pro1 is simply better. Lens choice is not really an issue, because I can put virtually any lens I want on my X-Pro1.
And the X-Pro1 does all this in a far smaller package than the 5D2. There's really no downside. I give up a few pixels, sure, but the X-Pro1 images enlarge better because they are sharper and have less noise. I also lose a bit of DoF due to shooting shorter focal lengths for the same framing, but I can't say I've ever really missed this.
Even a year ago, I wouldn't have said these things. But cameras like the X-Pro1 and X-E1, Nex-6 and -7, and to a lesser extent the OM-D (m4/3 is really pushing it in terms of DoF control and ease of enlargement) have completely changed the game.
If I were starting out, I'd be going mirrorless, all the way, unless I had a very specific need for a DLSR.