This argument has been done to death before. the answer, goes something like this..
"I refuse to prove that I exist,' says God, `for proof denies faith, and without faith I am nothing.'
"`But,' says Man, `The Babel fish is a dead giveaway, isn't it? It could not have evolved by chance. It proves you exist, and so therefore, by your own arguments, you don't. QED."
In pretty much the same way, the Amiga Operating system requires it's own faith for without PPC it will cease to exist.
Back in the midst of time (If I recall correctly) there lay another operating system called BeOS It too would install onto x86 alongside your Wintel partition and it too was a very good OS based on the original AmigaOS.
What happened? it died.
The argument went something like this...
"I want to play a game" - Boots into windows.
"I want to use MSN" - Boots into Windows.
"I want to check my hotmail" - Boots into windows.
"I want to use my webcam" - Boots into windows.
"Oh dear, I am running out of disk space, hmm, I don't use BeOS much, I'll delete it and free up some space"
and pretty much, that's why, such a good OS died on x86.
Now, with Amiga OS, if we don't want it to suffer a similar fate, has to be on it's own PPC architecture, Meaning that, if you spend £$€ on it, you may be tempted to use your investment and not leave it there gathering dust.
AmigaOS requires a bit of faith and some devotion to it, those who are faint of heart, should steer well away.
As to the x86 vs PPC Speed debate, it has been done to death already elsewhere, All I will say is that OS4 is fast, bloody fast, faster than my PC with Windows XP, (Barton Core) Athlon Based Chip with 512mb ram etc, etc.
I have thrown this out to many ppl here before, if you are in the UK and wanna see (and try) OS4 in action and you are in either, the London area or the Peterborough Area, contact me and you can come and see OS4 on my PPC based machine, at one of the usergroups meetings in those areas very soon.