OK, I'll give a mini-review, as a lefty with two of these knives.
First, the locking mechanism is no problem for a lefty - you won't accidentally release it, and with a little practice it can be easily operated by the first or second finger of your left hand. I find it a significant improvement over a standard liner lock, especially for us lefties. (If you want, you can ignore the release button, and use it as a regular right-handed liner lock).
The knife is well shaped, it my opinion. It is not TOO large, but with my large hands, is still very comfortable. The slightly up-tilted file work over the thumb stud makes for a great hold when gripping the knife for some heavy work. I find it easy to hold the knife and use all 3.75" of the blade, depending on the task at hand. The blade is ATS-34, and combined with Buck's edging, is razor sharp and keeps it.
Now for the downside for me, which was quality control. The first one I got was part of the original production run, and was marked "1 of 500". It would not lock up solidly at all, and I sent it back to Buck for repair, and they promptly sent me a replacement without this problem. Joe Houser immediately caught that my original production run had been replaced with another, and emailed me as to whether that was OK, or if I wanted the original knife repaired. After some thought, I decided to keep both knives, and pay for the second.
My original knife came back in beautiful condition, and is as solid as any knife I've ever owned. Unfortunately, the second, user, knife has developed a slight side-to-side wobble in the blade which is uncomfortable, and especially noticable for example when running the knife along a steel. It's minor, and I haven't wanted to bother Buck about it, but I find myself carrying the knife less that I might otherwise because of it.
In summary, it is a great knife. From my experience though, there have been some QC problems and you may want to buy it inperson somewhere, to make sure you are getting something that satisfies you.
