My main objection to Perl 6 is that it will be mind-boggingly complex, both in semantics and possibly in implementation. It's not about new syntax, new object-oriented goodness, new regular expressions, new what-not; it's about all those together. I have read half a dozen Apocalypses, several Exegeses, and I cannot comprehend how anyone could understand the whole, much less how it's possible to implement it without errors.

Of course, the counterargument goes that you, as a programmer, need not learn everything, that you can use only a subset of the language. But that's not the point. Someone (or rather several someones) has to implement the whole wickedly large language, and even so that 1) the implementation and the specification match, and 2) there are no (engineering) errors (bugs) in the implementation. Will it be humanly possible? I'm doubtful.

On the other hand, I'll be probably among the early adopters once the first usable version of Perl 6 will be released. It contains a myriad of improvements over Perl 5, and a plethora of improvements over other existing languages, including Haskell and Lisp. I fully expect it to become a hugely popular language.