If only his J.G. Jones' name was just J, then that pun would have worked a lot better.
ANYhow, as you no doubt have heard screamed from various message boards (that is how angry some folks are, you can actually hear their rage through the internet), J.G. Jones, who already had another artist come in to assist him with Final Crisis, is now so far behind schedule that DC had to get the great, awesomely talented Doug Mahnke to draw the last issue.
Which is a shame (mitigated greatly, of course, by the fact that the back-up is the supremely, amazingly skilled Doug Mahnke).
In any event, I don't think this is particularly a big deal. Jones sounds practically apoplectic about his regret over not being able to finish it, DC certainly did their due diligence with Jones, giving him a TON of time to finish it - it just didn't get done.
End of the day, Jones just couldn't get it done in time. Que sera, sera.
This is not the first (and it won't be the last) time an artist told a company s/he was certain s/he could get the job done on time and wasn't able to. This is not the first (and it won't be the last) time that a comic company built a bunch of lead time into a project so that it would get done on time and it was still not done on time.
In the end, I think DC did the right move by replacing Jones. As a work of art, I would certainly prefer Final Crisis to be delayed until Jones can complete it - but Final Crisis, much like Civil War, is not solely a work of art, it is a driving force of DC's entire superhero line - you can't just delay that, especially when the replacement artist is as great as Doug Mahnke. Hell, if they combine Superman Beyond with Final Crisis in a trade, it will look like it all was planned, even.
In fact, I remember taking issue with a piece written by a DC editor where he suggested that fill-in artists on big projects was not a tenable solution, and I recall noting that I disagreed with that, that I felt that if the project is important enough, fans WILL deal with a fill-in artist, and that is a better solution than major delays (only on projects whose timeliness affects other books). So DC is doing exactly what I said they SHOULD do, so I certainly can't complain.
So don't feel so bad, J.G.! This stuff happens, and DC handled it about as well as they could!