The two times I went to the festival in the past, I wasn't successful in obtaining tickets. In 2004 I was lucky enough to hear about a largely unannounced second sale from a friend who had read it on the NME website, and got tickets that way, and in 2005 I saw a notice for ddevents a few weeks after I slept in the day tickets went on sale.
I had a very good experience with ddevents, and would happily work for them a second time. I'd also feel a little bit bad committing to work for them now and then buying a ticket and canceling. If I leave it until after tickets go on sale I may risk them running out of places, especially as demand for work places is likely to shoot up at that point.
Ideally I would like to go without having to work, although working does add another element to the festival - the sense of being a part of it all, and meeting interesting people you otherwise wouldn't see - and getting an extra day out of it. It certainly isn't that bad a thing at all. Additionally I have at least two good friends who are really interested in working for the sake of saving £150 each.
Definitely a tough one.