Sorry that i didn't answer so long - i had a very busy weekend.

Sorry for such long post, but i have missed many interesting topics here
In the order:

1. Power usage. I believe that Telescope should not affect power consumption. Telescope is purely event-driven, it doesn't use any timers and has not any other regular activity. Thanks to XDamage extension, it does not any regular polls to acquire up-to-date window contents - X.Org server sends it to Telescope automatically.
Of course, if you will keep you tablet for long time with, for example, animated GIF in browser window, Telescope will receive XDamage events on every frame change, and it will do a minimal action on every event (but it will not do any drawings unless Telescope window is shown). But i'm sure that this minimal activity is nothing compared to browser's activity to show that animation.
So, i believe that if you will keep your tablet at night without any application running, or with application that will not do any regular drawing, Telescope will not affect you battery consumption at all.
But of course, if you insist that telescope does affects it, i will do tracing and profiling to check this, because power usage is most important concern for any mobile application.

2. Theming. Yes, as Kroll pointed, window decorations in Telescope can be easily themed by altering images at /usr/share/telescope/. You are free to even change dimensions of these images. But them, of course, must have same height.
But actually, i now thinking about dropping these images and implementing drawing of decorations purely by software, using gradients. This will give user ability to easily change colors of decorations without need to rerender and replace images. But it needs to be investigated how it will affect speed of drawing.

3. Accident appearing of Telescope after closing a window. Yes, i confirm this as a bug. The fix is ready and will be included in pending release.

4. Some ugly bars over the wallpaper in Telescope window. I tried hard to reproduce the bug (honestly!), but i haven't seen any bars. (Doesn't you call window previews and decorations as "bars"? As english is neither mine, nor Kroll's native language, it may take long untill we'll catch the joke). Accident appearing of telescope itself is fixed, as in #3.

5. More actions on hardware keys. I'm working on this. I hope with next release you will be able to assign any action on any hardware button (including shell commands). Addison: but if you want globally reassign +/- keys, how will you change the volume and zoom?

6. Pidgin menus change it's sizes. Very interesting, will post the bug and investigate it. As i remember, Pidgin's menus are n
ever matched my tablet's size