When I created panoramas previously I usually dont exceed 100 MegaPixel because it is good enough for (very) large prints and I rather have a perfect 100 MP version without seams and changing light conditions than a 1GPixel version with all these faults. Until some time back my hardware was also limited and large stitches were not an option. Now any decent desktop PC can easily be equipped with 12 to 16GB RAM and with a Windows or Ubuntu 64 bit version on a recent CPU, you get fast rendering times.
I just made a 550 MPixel (or 0.55 GigaPixel) created from 60 images shot with Canon 5D MK II and 7-200 L IS.
