I think as Windows 8 is still in preview/beta version, it is free & maybe forever. But, when the RTM version is released, you want to pay for it.
Take Care
No you are not forced to use it... if you look on eightforums.com, you'll see there are ways of disabling it via registry and/or file edits. Speaking of which... maybe I should I write a quick C++ console app to do that automatically.
My Computer
Computer Manufacturer/Model Number
iBuyPower Chimera X58
OS
Windows 8 Pro x64
CPU
Intel Core i7 920
Motherboard
Asus P6T Deluxe V2
Memory
12GB (2GB x6) Triple Channel DDR3 1333 MHz
Graphics Card(s)
ATI Radeon HD 4870 X2 2GB GDDR5
Sound Card
Integrated Digital HD 7.1 Surround Sound
Monitor(s) Displays
24.6-inch ASUS VW246H 20000:1 Contrast, 2 ms response time,