In fact, it's no longer fixed width, though it has a fairly wide minimum width - I went with the change that was suggested earlier.
I'm glad people like the theme - although I ran it past the other mods, it was essentially my own decision to go with it. Also, Jeph felt no particular attachment to the old theme and so just let me go ahead.
I had originally intended just to replicate the old theme, but when I had reached the point that the QC-old theme is now at, I realised that there were things missing that would be a huge amount of work to put right. That was the result of a poor choice, basing the theme on one that was developed for a release candidate version of the new software - I just hadn't realised how much more had changed in places that affected the theme (that's why the stuff at the top of that theme can't be folded away, for instance). So I looked again specifically at themes that were up to date, and this caught my eye, not least for the use of the orange which links up nicely with the logo.