Well, some of my thoughts and experiences have already been linked from another thread, it seems.
Suffice to say I consider the Walther 99 series (in all variants) to be excellently designed and manufactured pistols.
I've found them to be durable, reliable and possessing good ergonomics. The only quasi-compliant I might offer is that the backstrap inserts have never exactly fit against my palm, while the M&P backstrap/palm swell inserts offer a couple that seem as though they were made for my hand. That's just a personal observation. (Yes, I've tried the Glock Gen 4 inserts, including the one that adds a beavertail.)
While I always felt the Walther 1-year warranty for the P99's was a bit limiting, their decision to offer a limited lifetime warranty for American purchasers of the PPQ is a welcome bit of change in the way of customer service.
Walther has been refining and improving their 99 series concept over the years, too. There's been some changes in the design of some models, including some parts. It keeps getting better.
I've heard there aren't any immediate plans to introduce a compact version of the PPQ, but if they ever do, I wouldn't mind adding one to my collection to supplement my SW999c.