Definitely agreed that implementation has been spotty - although a lot of the kinks seem to have been worked out now, and scoring an upgrade on my flight tomorrow turned out to be completely painless once I learned to try the "Upgrade to First Class" link.
I'll always prefer to book Delta metal when I can, and upgrade reciprocity likely won't change that. AS isn't a bad airline, though, and living in Seattle it can be hard to avoid them in certain situations (in particular, SEA-SFO is nearly impossible to book on DL metal, and if you're time constrained an AS direct flight starts to look pretty attractive on other routes too...)
Now that AS elites are getting upgrades on Delta as well (which started a week or two ago, apparently), I'm optimistic things will be a bit more consistent from here on out.
Plus, the AS board rooms have pancake machines and soup. So full of awesome.