Other.
I'm slowly building a word document which will have every rule the players need. It uses useful hyperlinks, generates its own table of contents (and a tabbed ToC to the left), and I might manage to pull of an index, if I figure out a good way to automate it. It also combines all of the OGL stuff I need and the flavor text I want in a single document. That's useful to me.
A PDF, which I can't edit, change, etc. is worse than useless to me. For cutting and pasting rules, I've got the original SRD RTF files, and those work better for briefly opening, finding the source, and copying it.
As for the lifetime updates - I'll believe it when I see it. I don't think there will be enough sales to cover the cost of upkeep in the long haul; and hours spent doing that are hours NOT spent producing saleable work. It's an unstable business proposition, which means that it doesn't factor into my decision to buy or not buy.