I'm not a developer but I have been using the Toshiba e800 since it's release. Virtually every application with the exception of games pretty much works fine now in both VGA and landscape. Very few apps have trouble with the screen orientation. More apps exhibit difficulty due to the small font sizes in VGA than in landscape. The programs that allow user font size selection don't have any problems at all.
I guess I don't see this as a big development issue unless the program is a heavy graphic program like PocketTV, PocketMVP, etc.
James Kendrick* ...using mobile devices since they weighed 30 lbs