There seems a major philosophical difference between U3 and Portable Apps. U3 is very commercialized, only runs on proprietary U3 drives. Portable Apps is very open, runs on anything. I don't think putting .NET on a host is an issue, it often is already there
There also is no need for a Portable App installer, although it is nice. Without an installer, the current portable apps "add application" will add every .exe in the folder (if there is more than one even if only one is the app the user runs). The Portable Apps group is planning on fixing this such you can add just the exe's one wants and not need to delete ones not directly started by the user (shelled).
In reality, one doesn't even need to use the Portable App menu system with "portable apps". I use many "Portable Apps" such as Thunderbird off my main drive. Everything is in one neat place and and to copy to it a stick, USB drive or another computer.
Really, all that is needed for portable apps is every application specific item (including image files) be stored relative to the app's folder and nothing is stored elsewhere, including the registry. This also makes backups trivial, just copy the folder and any subfolders. I find them great even on my main drive. I can sync my laptop and desktop by just syncing one folder tree. No need to hunt through Documents and Settings App Data, Local Data or registry.
Clearly I'm a fan of apps that store everything in a single folder tree using relative paths. Drives are huge these days so even if there is a 2nd user on the system, they can just use another copy. One doesn't even need an uninstaller, just delete the tree! However, in this case, I really desire to take my photos on a USB drive.
Thanks for looking into it.
gerry