don't forget the $$$ for sliders (if you don't re-use your existing sliders) and side mounts. Here's my little "what to buy" guide
http://986forum.com/forums/diy-project-guides/34516-installing-gt3-seats-overview-options-hardware-needed.html
To answer the initial question:
I have knck-off GT3 seats in my car all summer and find them actually pretty comfortable
The fact that the seat cushions are attached (and can be also opened) via Velcro also allowed me to fabricate my own lumbar support (out of a piece of foam padding) and to install seat heating (from a cheap eBay kit)