I've been doing this since last December (with a little break over Xmas and New Year cos I was on holday). I've dropped nearly 2 dress sizes.
You definitely get used to the fast days and stop thinking about food so much, and I think it also helps to re-educate you about what a portion is - yes you can be satisfied after a small chicken breast and salad/veg and no, you do not need that pudding!
I find it also works psychologically as you can think, I'll have that cake tomorrow, and then often you find you don't really want it.
I still train on fast days, but find hard swimming too difficult and tend to stick to short runs, cycling and weights type stuff. I think there are benefits to training without being fully fueled as it gets you used to not relying on sugar during training/races to get through. Also the endorphine rush from running when you haven't eaten much is immense!!
Isn't it to do with how well you float. Women generally have higher body fat so we float better, floating better gives you a more streamlined flat body position in the water so you swim more efficiently. Using a buoy aids your body position so you swim more efficiently. I have also hear that over a longer distance the kick is a lot about keeping you level in the water so you pull better, but in a sprint distance is more important for propulsion.
I think it's worth trying to improve your kick, cos even if you're not going to kick loads you still want to maintain as streamlined a position as possible and get whatever help you can from the kick. Do you do kick drills?
Gellybean - the no ipod rule is for you own safety and that of those around you. Don't worry, the atmosphere will enough that you shouldn't mis the music, plus it will allow you to chat to others if you wish and hear the cheering of the crowd thatyou might miss otherwise.
For a HM I wouldn't eat any more than usual the day before, I think there's far more risk of getting to the start line feeling all bloated and causing GI distress during the run if you consume more.
Like MicknPhil I too would do something gentle the day before and have a rest day today, but each to their own and some prefer to rest the day before. A swim can alos be good to losen you up.
Or - sausage and bean hotpot - caramelise a couple of onions and perhaps some mushrooms, cook sausages then cout the sausages up, mixed with the onions and a tin or two of beans (depends how many people you have), bake in the oven and serve - with cheese on the top if you like, or a bit of salad and mash if you're really greedy. Add a little mustard to the beans.
As Cougie says - I tend to try and time it for a quiet week where I'm not racing and train in the day before an evening donation, then I'm okay to train again the next day. I wouldn't attempt back to back sessions after a donation.
I may be wrong but isn't also part of the reason for taking it easy that you can open up the donation site and find yourself bleeding badly??