Yes, to me "completely solves 1)" would mean using mono/etc for the other platforms and having a .net compatible system working seamlessly for all of them.
(Then you could get the same critiques as java web start.)
(Then you could get the same critiques as java web start.)
It's a great experience in Windows though. We have multiple internal applications running on it.
Although it's not a one size fits all solution. But internal apps that can leverage windows are extremely quick to setup with the winforms/click-once combo.
Shared network drive and everyone has an installation + auto update mechanism.
( But i guess that combo isn't popular here )