I somewhat share the sentiments of hardluk1 and EMcx3. Unless you already have a very strong affection for the PPQ, Walther, and striker-fired pistols I think you're unlikely to be completely satisfied with the Q4 SF. The price is very high - unless you're certain you love the Walther PPQ (which, from the sounds of it, you've never even fired) I wouldn't advise you to buy one.
With that said, the Walther PP-Q4 Steel Frame is a fine pistol. I find it very enjoyable to shoot and reliable as nails.
The pistol is very controllable and considerably less snappy than the polymer version. It only comes with one sized grip set with a rubber-ish texture which feels really nice in my hand and very grippy. YMMV.
The trigger is advertised as the 'quick defense' trigger featured in the poylmer PPQ. In my experience it is virtually the same trigger in both guns. I'm not a pro bullseye target shooter by any means, but accuracy was quite good especially with an attached RDS. I couldn't help but be left with the feeling that for a $1350 pistol I would have liked a smoother feel to the trigger than the $500 plastic version.
Again, it's a nice pistola but the competition in that price range is very, very steep and certainly worth taking a look at.