My favourite stitching program has always been Panavue's image Assembler. Whenever I've tried other stitching programs, they've either proved to be not as good, or if better, more cumbersome and definitely more time consuming (I'm thinking of expensive programs like the no longer available PowerStitch, or free programs like PTAssembler).
I'm trying to reduce the amount of time I spend sitting in front of a monitor, not increase it, so I have not tried PTAssembler. I have little doubt it can correct for perspective anomalies which IA might be unable to handle. However, for such situations I'll use my tilt & shift lenses, so for me, if I've chosen the right lens, there's not much that IA cannot successfully stitch.
Nevertheless, I was always disappointed that IA had a problem producing resulting files larger than 400MB (with Win98 it was only 250MB). There was also the problem of no 16 bit stitching.
Well, that's no longer a problem. Image Assembler version 3 comes in 3 flavours; Standard, Professional and Enterprise. The more expensive Professional and Enterprise editions stitch in 16 bit mode, support ICC profiles and image sizes up to 100,000 x 100,000 pixels.
If my maths is correct, that's 10,000 megapixels x 3 = 30 gigabyte files sizes in 8 bit and 60 gigabyte in 16 bit. This should be large enough for most purposes
There are no doubt other refinements in version 3. Previous versions were a bit lacking in the precision of the fully automated stitching option. One could try it, with little time wasted, but more often than not the results were not flawless.
First impressions are, the new version has improved upon the precision of automatic blending. I just loaded into the program a mosaic of 4 images which were in numerical order. All I had to do was specifiy that the resulting image would consist of 2 rows and 2 columns before loading, then hit 'run' and stand back. Within a couple of minutes I had a perfect stitch.
This program is so good, if I owned a Mac I'd be tempted to sell it and buy a PC