Trouble with wheel scrolling is it's hard to attach it to everything consistenly. Oregano has no scroll bars in frames so either it doesn't scroll, or you end up with all sorts of panes and dialogue boxes scrolling by mistake. Also the Scroll_Request wimp event doesn't support doing multiple lines at once so things go slow if you try to scroll Zap quickly
Does the USB mouse do scrolling horizontally with the wheel, and page up/down if you hold shift?
I've no idea about the nested windows used by browse. It's all fun though, although why anyone ever thought it was appropriate to use a mouse to scroll is beyond me, it just breaks everything