I'll chime in with some thoughts. I've only owned the stonewashed 0566, though. Overall, I think the knife represents an incredible value. You get a great quality piece backed by the awesome ZT warranty. To answer your questions:
1. I purchased the stonewashed version earlier this year, and think they did a great job with it. It hides scratches well and gives it a nice, roughed up look without looking too worn. The blackwash looks great as well, and I've been tempted to pick one of those up. Anyways, here's a pic.
2. The knife handles great. Hinderer knows how to design an ergonomic knife, and ZT is top notch in their execution. This model was designed with EDC in mind, and for that reason it rides low in the pocket and feels thin in hand, while still giving you a substantial grip. I wear size M gloves, and this thing feels great in the hand. As long as you remember it's a stainless steel framelock, you should be fine with the weight. It's a little on the heavy side for some users, but not for me.
3. Thanks to the blade being ground from thinner stock, it actually cuts surprisingly well. A lot of people complained about how thick the 0550 and 0560 blade are, and ZT definitely delivered a thinner blade. I cut everything from sushi to drywall with mine, and it never disappointed me. Keep in mind, it's basically a scaled down 0560 so it still has a substantial blade that will hold up to some prying and other hard use tasks.
4. I've owned an 0561, two 0550s, an 0551, and an 0801 and I can honestly say I've never had a problem with ZT's Elmax. It stands up to what I use these knives for, and does a good job at resisting corrosion and retaining it's edge. It also sharpens up pretty easily for me, but YMMV.
5. This is where it gets a little tricky. I personally didn't like the assisted opening, and took the torsion bar out immediately. I'm grateful that ZT gave us the option to de-assist the knife, as it works much smoother without the AO. Plenty of people complained that the knife was hard to deploy. Truthfully, it all comes down to technique. This rides on PB washers and is a Hinderer design. His models require more of a push button deployment, where you build up pressure with your finger and then fire it out. Using this method, I have 100% deployment every time. Check out the 0560s and his actual XM knives. Notice where the jimping on the flipper is? That's where your finger is supposed to go. Also, you need to make sure your other fingers aren't pressing down on the lockbar.
All in all, I would highly recommend this knife. Considering you can find them now for $120 and below, I think that's a steal. As far as which finish, all I can say is that the blackwash will hide wear better than the stonewash. In the end, it's all personal preference. Here a couple more pics for ya.
