Hi,
Welcome to 986forum.com
There have been quite a few discussions out there about this:
http://www.renntech.org/forums/index.php?showtopic=4503&
http://986forum.com/forums/showthread.php?t=3873
http://986forum.com/forums/showthread.php?t=3604
This one has some good tips for it you do the install yourself:
[
http://986forum.com/forums/showthread.php?t=2566&page=3&pp=20
The GAHH/Cabrioworld one had a few early on that had issues with the glass separating from the top, but that's been fixed (from what I can tell).
The Nachos Upholstery/Convertibletopsonline.com recently came out and is a bit cheaper.
I quoted out total cost top + installation at a few shops. The prices ranged from about $1200-$1500.
I'm strongly considering getting one myself. From what I have read about others that have it, they all like it.
Good Luck,
Larez2