Hi, all.

Sorry for joining the discussion this late.

My suggestion is somewhat different from what's discussed and may really be more suited for Inkscape 0.50 or later.

Suggestion: *STOP* treating guides as a special UI case and *instead* treat them the same way as all other objects in Inkscape. This enables reuse of all the powerful, existing tools for selecting, multi-selecting, moving, distributing, rotating, resizing (yes, resizing), deleting, skewing, setting specific x or y positions, moving guides between layers, and aligning guides to existing objects. Entering and exiting the guide editing mode could be as quick as double-clicking on a guide to start editing and double-clicking outside any guides to stop (similar to how entering/exiting a group works today). Even if there was a shortcut key for entering and exiting the guide editor mode,  it would still mean a lot less shortcuts to memorize. (Adding curves by dragging them from the rulers could of course still work as today, the two interaction patterns do not conflict)

Like Alexandre pointed out, aligning and distributing guides makes perfect sense. I've used this myself on multiple occasions, most recently while making game tiles for a children's board game but it's also commonly used to define layout grids for websites and the like. (And distributing slanted guides could work just as well as long as Inkscape imagines that they have finite length).

I.e.: Imagine being able to, for example, scale down the size of a large part of a design to 50% (including selected guides and all) just by using the transform dialog combined with the guide edit mode.

The current approach has provided quick progress in this area but, as we can see, we're painting ourselves into a corner by not reusing tools and by not utilizing different modes of editing, thereby hampering further progress.

Furthermore, reusing tools means more development focus on the existing tools, further streamlining the UI for them rather than distributing and diffusing development on more and more types of virtually identical interaction mechanics. ( one UI for moving and managing objects, another UI for moving and managing guides and so on )

In my mind, a common approach to almost all editing of on canvas objects in Inkscape would mean a reusable interaction pattern that's very familiar, powerful and intuitive for all users. The same interaction pattern can also be reused when some new kind of feature (like slicing of web graphics) is introduced.