I haven't looked at PTAssembler for quite a while, but when I checked it out previously it was nearly identical to PTMac. With Enblend for both programs, blending even challenging images is now fast and incredibly good. The biggest remaining problem with PTMac is that it's hard to place control point pairs accurately because of a serious (in my opinion) bug in the program. I keep pestering Kevin about it and he absolutely has to fix this before the program can possibly be marketed seriously. In any case, PTMac and PTAssembler need a LOT of work on the interface to make it more user friendly and intuitive, like Stitcher 4.0. If Stitcher had an option for manual selection of control point pairs like PTMac (but actually working right), I would just go for it, even at the exhorbitant price. As it is, I'm not going to waste a huge amount of time with my thousands of frames to stitch with any program that's too cumbersome. It's a little frustrating because I've got the parallax thing totally solved with a glued on 3.5 oz. panorama head that works perfectly for my 35 and 50mm lenses and some of my most exciting shots are for panorama things that will end up 20 to 80 Mpixels or so. I've done enough testing with PTMac to be sure that I can get perfect results that even Jack Flesher would be satisfied with. Fast, efficient, versatile super high quality stitching will happen, but no existing program is quite there yet as far as I'm concerned.
Other than custom making a light and efficient panorama head yourself, the existing options are not so hot. You can have a cheap, but unstable and much too bulky panorama head that's a hassle to set up every time or you can have a more streamlined head that is fairly easy to use, but extremely expensive and rather heavy. Without a panorama head to allow rotation about the nodal point of the lens you're very limited. You have to settle for rather poor stitches or only doing things with no subject matter close to the lens.
I'm looking forward to a 30+ Mpixel MF back with about 12 stops of DR, so that the hassles and imperfections of stitching or blending will mostly be history. I'll only need to sell my house to finance that too. Then I can be on the road shooting all the time, ha ha.