[toyg]

> Does it have to catter to every GUI toolkit there is?

To be a first-class citizen on "the Linux desktop", covering at least both main alternatives is a must.

> Mono developers targeted GNOME.

Thereby renouncing half the desktops.

>Actually the most popular Enterprise choice has been Gnome for half a decade or more

Maybe in the States. In Europe, KDE has long been the most popular choice for large deployments, which is why RedHat and friends still ship it.