Hi!
Before switching to Krpano I used Tourweaver. Krpano has loads of advantages, but the main thing which makes it difficult to learn at start is absence of Graphic User Interface. Let's put it this way: you have a car. With PTP you just sit in this car, press the throttle and drive. With krpano though you will have to understand the tiniest peculiarities of engine, suspension, gearbox etc. But once you understood it, you will show wonderful performance
In short, PTP is a GUI program based on krpano code, while krpano it is a pure code with plugins and to master it you'll have to at least read all of this:
http://www.krpano.com/docu/
If you're programmer, you'll get along faster, if not it could be confusing and sometimes requiring asking loads of questions here on this forum. Another main reason why, for instance, Russian/Ukrainian virtual tour builders have difficulties in learning this documentation is that it's entirely in English/German. I was lucky as I'm interpreter by profession

. Which means even non-programmer can master Krpano.