My own personal opinion:
The Krpano viewer is a standalone player that does not require the tools to be used. HOWEVER, use the demo tools for a week and you will wonder how you ever got along without them. I have seen several people on this board buy just the viewer and tools to save a few bucks, then later on they want to change to the unlimited domain version. My view, buy the unlimited domain version and get the tools included in the package.
One of the great things about this software is you can demo it until you are ready to make a decision. Try creating your panos without the tools if you like. If it works for you, great. However, do try the tools also.
Demo limitations:
krpano Flash Panorama Viewer
• it runs only locally or on a localhost server
• it shows a demo watermark
krpano Tools
• watermark in the output-images
• a short waiting time after processing
Many answers can be found by using the links on this page.
http://krpano.com/docu/