@donnacha | WordSkill - Or, a completely alternate route — don't pay anything at all for themes. There are quality, free themes out there.

Your comment reads like a big, honkin' promotional ad for StudioPress. While praising others and arguing price points is all fine and good (I completely agree that the price is steep), let's try to keep the facts straight and not bend the truth in our favor.

ThemeGarden customers will only continue to have working themes if they keep buying subscriptions.

You mean they will only continue getting updates. Let's clear that up. The themes, from what I can see on the site, will continue to work after your subscription is up.

The chances of a theme not working with a WP upgrade are pretty slim. I have themes I coded for WP 2.3 that I know still work.

...which received an enthusiastic review in Aaron Brazell’s detailed comparative review, a fortnight ago, of the four leading frameworks.

Of four leading "commercial" frameworks, two of which I wouldn't even consider frameworks.