Heatbed insulation benefits?

I noticed my Sidewinder X1 printer has some foil and foam rubber insulation on the bottom of the heatbed. I'm going to replace the bed with a new one and a new silicone heater, and I wonder if the insulation is really important or necessary? Has anyone tested the difference in heat-up time or power draw with or without insulation? It seems to me the silicon heating pad by itself forms some level of insulation. I think the foil insulation will be really ugly so I'm basically trying to avoid it.

I use foil baked insulation on the bottom side of my heat bed. The bed seems to heat a little faster, seems to be a little more evenly distributed, and seems to heating less often. ( more noticeable in the winter.)
Be sure to re-tune your heater controls after install.

Although I have never verified this with anything like thermal imaging. - Shane