CHUD recently did an episode of their podcast that was a feature-length commentary of the film, which was pretty funny and mostly focused on how the guy that made it was never heard from again. I think it was "CHUDdotcommentary #2" (#1 is "Taken" and #3 is "Prometheus"), and it's worth a listen!
Sky Captain actually had pretty solid critical reviews. It's sitting around 72% on RT. I hated it the first time I saw it in the theater, but I recently rewatched it and it wasn't as bad as I remembered. There's next-to-no plot, but it's basically an homage to 30s-era serials which were also pretty low on plot. It does have HDTGM favorite Bai Ling, though.
I think it's not a bad film- I think it's a really unique experiment that the How Did This Get Made crew could really have a lot of fun with. Not all their movies are stinkers- for example the recent Devil's Advocate isn't considered a "bad movie", but they can certainly find the outrageous parts of it to talk up.
I'm just referring to the 'digital backlot' aspect. This was the first of those to come out, and it definitely functioned as a 'proof of concept' for the studios.