Pete Prodoehl has done a script much like get_enclosures called renko. I downloaded it and it worked well. It’s easier to install than mine because he includes all the modules you need in his distribution, so if that’s an issue with you by all means go get renko.
He also points out in a post that the correct place for all this stuff to be happening is in the desktop aggregators like NetNewsWire and Shrook. It shouldn’t be too hard – have an enclosure preferences that lets you decide to download all enclosures automatically, only ones of specific MIME types, none, ask every time, etc. Set up a directory where you want them to go, click a check button if you want them automatically added to iTunes and away you go. For me, the only big issue here would be if NetNewsWire added this support. I’m already paid up on Shrook and I like it, but if this functionality gets added to a competitive product then I might switch.
This kind of thinking has occurred to me as well, which is why there is an upper limit to how much effort I’ll ultimately put into get_enclosures. The best script in the world pales to mediocre support in the desktop aggregators. There are one or two additional things I’d like to add to it, and then I’m probably going to slow or stop work, only fixing bugs as they are brought to my attention. We’ve now done our work in validating the proof of concept further, and it is time for the aggregator developers to step up next.