I wish I could say that I'm dumping the standalone player for bigger issues than my own impatience, but I can't. I hate having to wait the couple of minutes it takes to boot up the damn thing. That's really my #1 issue.
The sound is nicer on the standalone, but with my receiver/speaker set up I don't notice enough of a difference to care too much.
The picture is just as good on the 360 add-on as the A1 plus I don't have to put up with the occasional HDMI goof.
I'm losing the upconverting SD feature, but I can't really look at standard DVD now anyways. Finally, the 360 add-on is cheaper.
You are pretty much right on the mark. The 360 add-on isn't as good overall as the A1, but it's good enough for my needs at the moment.