It depends. It'll probably be a while before CNG can finish it, since there's an awful lot of coding involved, but if he thoroughly debugs it and follows through with it, then it'll probably be a lot less buggy than Essentials. That only leaves the issue of having to re-learn all the methods, scenes, etc. It's a bit of a gamble, but I wouldn't go as far as to say it's a bad choice though.
That's a pretty random error message. It doesn't even tell you what went wrong. I sent you the whole kit didn't I? The safest and surest thing at this point is probably to port your stuff over into the kit I sent you. And just in case, only port a few custom scripts at a time (starting with whatever menu system you're using, of course), and see if any of them break it. That way we can narrow down the cause.