Can you define "much much better" in concrete terms, or is it just a matter of assumption that 2nd gen >> 1st gen?
I wouldn't buy an ipad brand new today; too close to announcement/release of the next gen. If you have a good reason to buy now such as planned travel in the next month, I think its reasonable to buy a 1st gen off Craigslist if you can get a good price.
IMHO it's usually a good idea to wait a couple months after release before buying. Gives time for the accessory market to develop more/better options and time for any early production run issues to be sorted out. I have no problem letting others be the first in line, though I remain puzzled at the fascination with watching youtube videos of someone opening a box.
So if the 2nd gen ships in April, then May or June would be the time to buy. I bought a used ipad for a good price three weeks ago. The difference between what I resell it for an what I paid will be my cost of ownership over the four+ months.