I'll answer the original question directly.
I paid UKĀ£30 for OS 3.9 for my A1200 68060.
I downloaded the two free Boing bags to make it 3.92 or whatever you want to call it.
I like the OS because it is so fast and comfortable, but 680x0 is not the future unless someone starts making them in ghz instead of mhz.
I would buy another update but only if it were cheap. I need that money to put to a PPC Amiga, and so should other people. If no more 680x0 hardware improvements are made, the machine will fall behind more and more. I would not use, say, an Atari XE with 128k RAM and a floppy disk drive in 2003, but in a few years' time, my current Amiga will be like that is now.
Tip Of The Day: in British English, US spellings are acceptable only as proper nouns - Pearl Harbor is a harbour, the Medal of Honor is for honour, etc.