I'm a bit of an odd one, in that I'll donate to an ongoing serialization, but won't actually read it until it's finished. I found that the waiting drove me nuts, so while I've donated to both Fledgling and Saltation, I haven't read either one, and won't until they come out as books. As for what format I'd prefer if there's a copy given in return for donating, it's a toss-up whether I'd prefer electronic or physical format. Though for electronic format, PDF makes me shudder - they won't work on my PDA well, and are a pain on the computer. I'd happily buy an electronic copy from webscriptions though, and get a physical copy for a donation.