Well, for a number of really strange reasons I have a Walther P99 DA/SA style that I have put probably more than 10,000 rounds through. I also have a Glock 19 which is, more or less the direct competition, and have spent a good deal of time shooting, XD/XDM's (because they are cheap and plentiful), FNP 9 (because they are nicely ambidextrous) and the M&P 9 (again cheap and plentiful) because I really, really want to like them. But I don't. For other reasons.
Here's my read:
The Walther P99 is at least as reliable as any of the other pistols. There are possibly some batch issues around when SW took over assembling them, but I have never seen a credible report indicating that reliability problems were anything more than abberations that the factory would take care of. Mine actually is one of the last made in Germany and imported into the US by S&W and still has the Walther roll mark without the S&W one.
For me personally, it points and indexes significantly better than the other pistols and the site picture works well. Fundamentally, this means that I am faster to first shot on a target with this from the bench or draw than with the others. The difference to me between indexing and pointing, is that natural indexing means it is easy for me to grab it and be in the right grip. Pointing means that when I am in the right grip and bring it into my field of view the sights are already lined up.
Again, for me personally, it is a noticable amount more accurate and more forgiving than the other pistols, which means my groups, particularly at distance are smaller. This is not an uncommon experience for people who like these guns. It is one of the few guns I can play "the smiley game" with out to 30 feet. (The smiley game is where you take the small round Birchwood Casey target spots that are all black and make a smiley face on the target. Your buddy does it too. Then you take turns seeing at what distance you can nail the smiley with X number of shots. Furthest distance buys dinner)
I also like some of the features - it is a striker fired DA/SA with second strike capability and a decocker. The decocker is flush mount on the top of the slide so it is really hard to accidentally trip it. If you do, it takes a very, very small movement of the slide to set it back to SA. (Some don't like this, I actually do) The trigger also has a really short reset, which isn't the case with the Glock style triggers out of the box.
Now, the flip side - the trigger is heavy in DA and has a long take up in SA, which doesn't matter if you learn to manage the short reset for strings of shots. There doesn't appear to be many (if any) people that do trigger work on them. With the other guns, particularly the Glocks everyone and their brother will work on them for you and many kits are do it yourself.
So, the trigger is the only thing I would really change on the pistol. That represents custom work I would do (or have done) on ANY of them. It just so happens I can't find someone to do it on a Walther. Mine is 9 mm, and I don't see the 9 vs. 40 argument the same as some on the board do, so I've got no problem at all carrying it in 9 or better put, I would choose to carry it in 9 over other choices in 9 or 40.
While they aren't as popular, they are plenty capable as a CCW. Further, if you happen to like the particular set of features (striker fired with second strike capability and DA/SA with decocker vs. Glock action) it is about the only game in town. (I think Taurus now has something with a similar set of features, but I haven't shot it)
Thinkingblade