David,
I like my A2 a lot so far. I never played much with the A1, but based on my reading, the A2 is quicker and less buggy (and mine has worked perfectly so far). I can't compare the upscaling vs. my 3910 because I connected the A2 via component cables, and it won't upscale over component. My display has a DVI input, and I read there are some handshake and BTB problems with the A2 when going HDMI-to-DVI, so I never bought an HDMI-DVI cable but rather simply went component for HD-DVDs (and will stick with my 3910 for upscaling SD DVDs and for SACD/DVD-A). I have played an SD DVD on the A2, and it looked very good (although not quite as sharp as the 3910, which I like better for SD DVDs), but again, that is outputting 480p from the A2, not 720p or 1080i, so not a fair comparison with the 3910.