Which, today, I did.
I went to the huge, enormous, glorious and over-stimulating Apple store on 59th and Fifth Avenue, and managed to query just the right person for me to talk to--a charming and volulable young gentleman who (when pressed) could tell me what I needed to know to make my final decision in a way I could actually understand. I'd taken my old computer along, so whenever he asked me a question about what I already had, I could just refer him to the thing itself, which turned out to be very useful. Of course, getting home with two computers just at the beginning of rush hour was a bit of a challenge, but I found an off-duty cabbie with bowels of compassion, so it was really my lucky day.
My new computer is beautiful and fast. I bought it a green shell (everything green (in our life, anyway) belongs to me) and an external hard-drive so it can remember things in case the computer forgets them. Now, all I need to do it try and ensure that everything that was on the old one is on the new one, and learn to use the things the old one didn't have. .
Wish me luck/