Hey m29fan. I just took delivery of my new M29 today and thought you might benefit from a quick review of it. Mine has the blued finish and has the 6.5" barrel. It's a beautiful weapon and is sweet to fire, though after 42 rounds I have to say the grooves in the back of the stock made the palm of my hand feel a little tender. It also drew plenty of attention at the local range this afternoon. Someone near me was firing a .22 pistol of some sort and I could barely hear their shots with my ears on. I promise you won't feel that way about your M29!! I am quite sure the guy next to me enjoyed the muzzle blast for all those rounds. I sent my paper target out 15ft and the muzzle blast was causing it to sway in the breeze, some times a lot. My 9mm can't do that.
Also, I am not a well seasoned shooter. However, I was pretty much able to put holes in my target within 1 to 2 inches of where I was aiming. I can't do that with my Glock 26 yet and I have more experience shooting the G26. So, I have to say, this is a very accurate weapon as well. I used Winchester USA .44 Rem Mag JSPs and they seemed to work decently and accurately.
I was slightly disappointed that I actually had one problem with mine today. Toward the end of my range session the trigger started to stick all the way back after firing. I had to manually push it forward. It didn't happen every time, but pretty disappointing. I asked one of the staff at the shop about it and he said it could just be b/c it's new and not broken in yet. He suggested if after a couple hundred rounds it still does it to call S&W and get them to check it out. Hopefully he's right and it works itself out.
As far as the lock mechanism is concerned, I don't really feel it's a big deal. It could be a nice feature if you have children around. But certainly didn't have any negative affect on my enjoyment of the weapon while I was at the range. I am not going to lose any sleep over it, that's for sure.
As far as new -vs- vintage goes, I decided on a new model b/c I want to be able to take it to the range and shoot it when I want and not feel like I should be keeping it locked away and pristinely preserved.
Best of luck and I hope this helps in some way.