I just purchased the five-inch CS Gunsite from wholesalehunter.com (lowest prices anywhere), and I love it.
Everything I thought would be good about the knife is. The blade is of course top-notch. The fifty/fifty serrated blade is very usefull, and the serrations very effective. The length of the knife was at first awkward, but now I carry it without noticing its presence. It does small and large jobs great, and takes an incredible edge (came with one too). No complaints about the tanto style blade, but I don't see much advantage over clip either except for the untested tip strength.
The points of the knife that I thought would be week spots were not, thankfully. First, the Zytel handle is plenty rigid--no flexing at all (then again, this is a large knife, so the smaller ones may not be as rigid). Also, I have not been able to make the lockback mechanism fail. The plastic pocket clip was the biggest surprise: It is great. It is much more incospicuous than a steel clip and is designed very well. Unlike the above comment, it looks very sleek and is much tougher than any other non-metal clip I have seen.
Unfortunately, the knife came very tight. I have had it for a couple of weeks and it took almost that much time for "flicking open" the blade via thumbstud. It is okay now, but will be better in a couple more weeks. Other than that, it does feel smooth with a definate, crisp lockup.
My friend has a BM AFCK which I always loved and borrowed just for playing with. I have to say that I'de rather have the Gunsite than the AFCK even though it might not be as cool. It's as good a tool, costs less ($48 for my gunsite after much hunting), and is in my opinion a better weapon.