I have a few suggestions regarding the handling of tileset and zoom factor in the TF interface. Since these suggestions may not make sense on their own, I'll start by describing the situations which prompted them.
First, there are times when I wish I could manually control which tileset is being displayed, independent of the current zoom level. For example, my preferences are set so that a zoom of 8.88 maps to Topo 16M, but for this particular map I'd rather use Topo 4M. You can sometimes force TF to do this by messing with the preferences, but not always.
Second, I often wish I had a way to switch to an exact zoom level. Relative zoom is nice, but I find myself wanting to reset the zoom to a specific value every so often (most commonly, 1.0). The tileset selector provides a partial solution, but only if you are changing tilesets. If I'm using Aerial 4M, and want to jump to 1.0 zoom, I can simply select Aerial 1M. The tileset is changed, and the zoom set to 1.0. But there's no easy way to set the zoom to 4.0 when using Aerial 4M; selecting Aerial 4M does nothing as that is already the current tileset. Instead, I have to change tilesets twice: away from Aerial 4M, and then back again. This is frustrating, especially on an old computer like mine, which is painfully slow at scrolling scaled maps.
Finally, a related problem shows up when editing tracks. I'm examining the map, and see something which bears closer inspection. I zoom way in, and disentangle some trackpoints. But when I'm done, there's no easy way to get back to the view I just left.
The first two of these are easy to fix--at least from a user interface perspective. One normally wants the tileset to be linked to the zoom level, but not always. One could add a checkbox between the zoom level and tileset droplist which controls this linkage. When checked, TF acts as it does now; when cleared, zoom and tileset act independently. To easily control the precise zoom factor, one could make the zoom display control a combobox; the droplist would contain common zooms (0.25, 0.5, 1, 2, 4, 8, etc.), and the user could type in an exact zoom level.
The last item is slightly harder: it implies a history of views, with the ability to move back and forth between them. The metaphor used by web browsers may be of use here. One has the current, live view, and a history of saved views. Buttons allow one to move back and forward through this list, and to push a new saved view. Moving or zooming makes the current view the live view, and discards any "forward" views from there. One could even get fancy and allow combinations like holding the SHIFT key while zooming with the magnifying glass to automatically save the view before zooming.
I know this was a pretty long post, but I think these minor interface changes would improve the ergonomics of the interface greatly.
