I know the glass windows are nice and that is what we have on ours.
I do miss the plastic window with the zipper .You can lay it down with the top up and get air flow
You can unzip it lay it flat with a towell under and over it and with top down you can store a few items on it if you need to
We had a long tall but real narrow ice chest that we could set over the back .The glass window will not allow that ,we are afraid it may break

 

I have a 2001 Miata and my rear glass window just fell out. I think it was due to the heat here in Florida. My top is in excellent shape so I just need to find out how to put that window back in. It is not broken.

 

Its probably cheaper to just put a top on it that has a solid glass or a plastic window.

Last top I bought off ebay was a solid glass for an NA it cost me 185.00.

I see now the same top is 259 with a plastic window.

If your top is the least bit bad its better to replace the top when you go to sell the car having a new top will help you sell the car easier.