I could afford a digital back only if they would drop in price to something around the current price of a 5D to 1DMKII (and even then who knows how the money is in a year's time).
I also had to consider the cost of film unitl I could go digital with a MF setup, and import/VAT on the camera if I got it from the USA (e.g. used equipment from B&H).
I got the 5D from the Canon outlet on Ebay.co.uk. I've delt with them before and not had any problems, it cost £300 less than you would pay for it new but comes with a 1 year warranty, it could be a demo with no use or maybe a returned item that had a fault fixed, I'll see when I pick it up at the weekend.
The plan is to now sell the 20D and get a used 1D MKII(n), that will be for high speed stuff, while the 5D for landscapes etc. An advantage of the 5D is I can also use it for a light weight set up when I don't want the weight or attention you would get with a 1 series or MF.
I could wait until PMA, and then maybe end up waiting until I could afford the new gear, but I want to take pictures, not be looking through websites. Who knows I could still end up with a MF set in the future, but for now I can't wait for 5D to arrive, with my 20D still away for repair it is nearly 3 months since I last took some photos.
You said you could afford a digital back in a year? I can't see the point getting the 5D now. Canon will launch their new model this year. Tha 5d's price will drop ( specially on Ebay) and rolley is launching the hy6 (the digital backs will cost less too) but anyway... good luck!