I think its probably a bi5 big for a backup gun, but might be very attractive for concealed carry. I've been pondering getting a CZ RAMI for some time now, and the p224 might be a game changer for me (by way of reference, my main carry pieces are the p225 and p229).
P224 CZ RAMI
Weight 1.6" 1.6"
Length 6.7" 6.5"
BBL length 3.5" 3.0"
Height 4.5" 4.7"
Width 1.3" 1.3"
Capacity 12 10/14
Again however, I think I'll wait a bit to see what the market feedback is, let Sig work out any kinks, and hopefully Sig will also offer a SA/DA in 9mm in the near future...