I’m thinking of switching to a Mac, and I’d like your advice

I blame a series of developments for this. First, I can’t forgive that virus known as Windows Vista and the manufacturers who foisted it on us. Second, my iPod turns out to have been a gateway drug. It’s just a thing of beauty, and I’m still amazed by its functions and capability, all fit into such a tiny object. Third, my old Dell is about dead from sheer exhaustion. I’ve preliminarily settled on a Macbook Air, and am leaning toward the 11-inch screen version for blogging on the Metro. So, what’s your advice on the following:

1. What’s the best place and time to buy one?
2. How tough the switch is going to be, in terms of adjustment and compatibility?
3. I don’t do gaming. As if. So is it worth it for me to upgrade from 1.4 GHz to 1.8 GHz?
4. I often have multiple programs open at once, including Google Earth, which takes up a lot of RAM. I suppose that means I should upgrade to 4GB?
5. Do Macs work with most commercially available wireless internet services? Or is there some better option for going wireless with a Mac?

Thank you in advance. Hopefully, I’ll repay your advice with more and better output.