I downloaded the T1i manual & product guide from Canon's support site, and put them on my iPhone for reference. The paper manuals are small, so the PDFs are quite readable on the iPhone.

According to Canon, due to the T1i's smaller-than-35mm APS-C image sensor, my 55-250mm telephoto is equivalent to an 88-400mm 35mm lens.

In normal use, Medium/Fine (3,456*2,304) is indistinguishable from Large/Fine (4,752*3,168), although I haven't yet tried Normal JPEG compression, which will probably also be just fine at about half the on-disk size.

I haven't used 1920*1080@20fps video (the T1i can't do 1080@30fps) -- instead I use 1280*720@30fps (222mb/minute, which should fit 73min on an otherwise empty 16gb card), but I am fortunately satisfied with both video & audio quality, despite the tiny on-body microphone (no audio input available). I'm not very conscious of the resolution (even though it's easy to see on the rear LCD display), so I need to get used to raising it to L for long/landscape shots and returning to M for normal/close photos.

Unlike the SD800 IS, the T1i is somewhat awkward in portrait orientation -- especially with the LumaLoop's lanyard hanging in front of my face. I like the LumaLoop, though.

I use BetterHTMLExport for exporting galleries to the web. Today I hit a new problem: my private December photo gallery is 849 photos, mostly a mix of uncropped Large & Medium T1i photos. The whole thing (including full-resolution images) is 3.2gb, and for some reason Mac OS X sees my private Samba share as an 8gb volume with 2.8gb free (it's actually 634gb with 198gb free). I've noticed this before, but it never mattered except when copying large OS installers up to my archive. Today I had to export to a local gallery folder and then copy it up to the server, because iPhoto refused to let me export 3.2gb to a volume with (apparently) 2.8gb free. Not BHE's fault, but annoying!

Update: I tested in-camera JPEG compression. Large/Normal and Medium/Fine are both very good, while Medium/Normal isn't quite as legible at 100%. Interestingly, Large/Normal images are smaller than Medium/Fine, so I'll use L/N. Bonus: I won't have to switch resolutions between landscapes & head shots.

As Ken Rockwell points out, video is compromised by how well the in-body microphone picks up noise from lens movement. So 'autofocus' (which must be manually triggered by hitting the AF button) and zooming are both quite disruptive.