I like this a lot (only with the signature features), but if you have a nice shiny GUI program (which PAR is GREAT at bundling), I'm wondering how easy it would be to funnel PAR connection errors up into happy-shiny-GUI land...as well as whether one could produce "do want to upgrade, etc" type GUI's...

If you wanted to upgrade a whole application this way, it would be fairly easy to have a simple shell with a go() method and have PAR download the entire application, then invoke the "go()". That way you would be free to completely rearchitect your app rather than fixing yourself to certain unbrekable interfaces.

I'd probably just implement my own system though, with the launch.exe and a seperate goforthanddostuff.par ... and code my update interfaces around that. (preferably sftp with public keys that ship with the product, or something like that?)