Well, considering that at some point, they re-release the PDF with the corrections, then it's not really.
It might be just me, but I didn't get too many updates on my PDFs ...
I've gotten updates on all the PDFs I purchased through DriveThruRPG, BattleCorps and Paizo when the original files have been updated from errata and such.
I still recall a time when most of the typos in CGL product were caught before the PDF was available. I think we called it 2009. Books weren't perfect, but they weren't War!
It's pretty common place for video game companies to ship a game in late beta and expect people to sit and wait for the patches, or make their own, when they run into trouble. It's accepted, but it's sloppy. And it should not be replicated in book publishing. If you're going to put up a beta, then do what Minecraft is doing. Put up a workable beta, charge a small amount, like half price. Anyone who wants to can buy in early and gets the future updates for free. Once the product is finished it goes up for the finished price.
I appreciate the fact that PDFs get updated, but it shouldn't be abused to put out unfinished product early.