I was going to start writing an image gallery browser as a java applet (all the ones available for my current CMS system are broken, crappy, or not free).
Do most users have java support? I know at least one friend for which java applets can never load. I don't know if it's wiser to do this in flash. I'd prefer not to though as the dev environment is not free for flash, and I don't know if more ppl have the flash player plugin than people do whatever is necessary to run java applets.