Stephen; You are showing the typical swinging mood buyer behavior that is quite natural and expected, before seeing that one aggressive sale pressor (Person) that can sell you what ever he has in the store.
So as long as you have the decisive power (Money in you wallet), make sure to do your home work fine.
If you finally decide on Mac, you may still think over as if you have noticed hopefully, the Tiger is getting absolute or at least old as Leopard is on the way. On Christmas Apple store told me for spring/summer.
LINK
You don't want to buy something that you need to upgrade in a month or two. So if settling for mac remember to delay your purchase a bit as you will get the newer OS at no extra price (Unlike PC mac won't upgrade you free for soon to appear OS).
Sorry if I was more of decision-obstacle maker than helper, but just wanted to make sure you know all your options.