Although Errors really bug me....
I can deal with them if they unless they are on the level of Mongoose's Ultimate Monster 1 or Goodman's Primeval Groves.
A few minor errors is fine. If I know about them! If a publisher releases an errata sheet later & tells me all the errors that crept in. Fine, I can go through with a pencil & make the corrections. (as in MM3).
As long as the book doesn't look completly re-written by the time I'm done. The problem is that many publishers don't release errata sheets (even when all the problems are mentioned by someone like Cooper). Thus I either have to go by those errors others have found, or try to hunt through and find them all myself.
Having finished ME1, I can give it a 'it's ok' mark right now. I didn't a lot of errors, but I wasn't looking for them. If I knew Mongoose would later put out an errata file, I'd probablly up my 'it ok' to 'a good general monster book'.
PS. I was going to Rant about how I hate companies that release an 'errata' sheet with like 3 things, when a product has dozens of errors. I was mainly referring to Goodman Games Primeval Groves, which I was pretty sure had really horrible monster stats, in addition to the editing errors they released a errat for. But, I don't have it handy, can't remeber for sure. Thus I will not condem a product or company falsely.
Expect a follow-up tonight.