There will always be errata. I'd suggest getting the second printing, just to reduce the number of the errata pages you tuck into the back cover.

Waiting for a third printing is a mugs bet: HOP is a printed by Morgan Freeman, they may not issue a third printing unless there is a really massive demand for the second. The first printing of HOP was something like two-thirds pre-sales. A lot of people ordered it online with 'ship it to me when you get it'. That demand really surprised the folks at MF, they are not used to 'text books' selling out like Fiction. Unlike O'Reilly, they don't print in small batches, so they can't fold errata in at will. MF did a first printing of 1,500 (if I recall correctly); the second may be as large. (MJD had the actual number in one of the final postings on the plover-hop list, but I don't have the message handy.)

I have a first edition on my book-shelf here at work, with the errata sheet tucked inside. I can live with that. Eventually, the entire body of HOP will be available on line for perusing/downloading. (Eventually being early next year, as I recall.) That may well serve as the 'third and final' edition.

As to is it worth it? I think yes. Slogging through HOP took me a couple of months. I can't read tech-lit like I read SF or a Mystery. I read a few pages at a time and let it percolate a while before I start the next section. I read through HOP to get a feeling for a different way of approaching a couple of different classes of problems. I find that I sometimes have to really work at understanding MJD's code, but the Ideas he implements in his code are facinating; and, once I see what he is driving at, the techniques turn out to be aplicable to a lot of the stuff I am facing at work. I expect to revisit the 'parsing your own language' section again and again as we rewrite a particularly old and convoluted protocol we use on our internal server farm.

There is a lot of neat stuff going on under the covers in HOP. There are a lot of neat little tricks in HOP that I can borrow and use. To me, learning how tail-recursion works and seeing it in action again and again was worth the price of the book and the long wait for it to appear.

=================================================

Update -- The publisher is "Morgan Kaufman", not "Morgan Freeman"! (I saw 'March of the Penguins' over the weekend....)