Just a hint to folks: you can work around the lack of Alpha-blending in GUIs by using a character as a GUI! It will take some scripting to ensure it stays in the same room and to hanlde click (probably best kept to simple GUIs) but you could even make an inventory with this system!
Of course, CJ will soon implement alpha blending in GUIs and render this hint nearly obsolete... ;D
Yep, alpha blended GUIs is something I intend to add for the 2.6 final, but using a character will let you get away with it for very simple GUIs in the mean time. Of course, you don't have any of the GUI facilities if you use a character :P