Well, AJAX Design Mode is still in beta...if you've found problems, I would suggest reporting them to QlikView so they can resolve it in the next SR (email@example.com). Or do you mean that AJAX clients are having problems?
Horizontal mode does not work in AJAX. AJAX isnt quite the same as the app but its getting closer. We have been using AJAX for about two years now. We have had sonme issues but were able to work through most of them. I have a post somewhere on here about the horizontal mode, if you can find it in the search, let me know, I may be of some help.