I also use elmer's purple glue stick and it has been so much better than aquanet hairspray for me.  With glue stick and a full enclosure, I have printed an 8 hour object with sharp corners that took up most of the bed without a single hint of warping or lifting.  Then just let it cool and it pops right off and I have a smooth finished bottom layer every time.  There is no mess like hairspray and it won't get all over your rods.  Your glass bed wipes clean with water and a rag easily.  You can buy it practically anywhere, I pick up a stick the same place I get my groceries for less than $2.  I have 50+ hours printed on my glass bed and it still looks like new.  Every time I convince someone here to switch to glue stick and put away the hair spray (except for the initial stick of glass to kapton covered bed), I feel like I have done my good deed for the day.

2. Any glass will be fine, but if you're using regular glass be careful not to take it out of the printer and stick it under cold water etc. (i.e. avoid sudden temperature changes). Certainly nothing particularly special about the solidoodle part. People here have used mirrors from Ikea and reported they work well - cheap, pack of 4, rounded edges, right size for SD3/4: http://www.ikea.com/au/en/catalog/products/00192594/

3. It goes straight on top of the existing bed - leave the existing kapton on. Bill is using clips, but since wardjr suggested sticking the plate to the bed with more hairspray, I've been a convert. This ensures no warp in the glass plate, and is still pretty easy to snap off when you need to take the plate out.

1. Do I need kapton tape for it?  Can I do without?

2. Is it borosilicate glass?  Doesn't seem to say that specifically in the description.

3. Do I have to do anything other than just lay that on top of the kapton tape of my aluminum bed, or does it replace all that entirely?

And if anyone else has done this specific upgrade, I'd like to hear from you.