I've put a
new page on the Wiki aimed at all the posters asking "why does my heat bed take so long to heat", it's just meant to answer some of the commonly asked questions.
Feel free to comment, or disagree with my conclusions (I'm still learning this stuff too).
Tim
Printers:
Prusa i3 (plywood box frame)
RAMPS 1.4 and Arduino Mega
Mendel 90 (sturdy)
Smoothieware
My RepRap Blog