I gave up waiting for the Sony. I went out and got the DTC-100 last weekend and I'm glad I did. It sure beats "imagining" what Hi-def looks like as I would have to with the
vaporware Sony.

(Rumpole - like you I have the 36XBR400.)
As for the DTC-100 not having the APG I don't find this much of a problem since I programmed my Pronto remote to do the switching for me. The Pronto may be something to consider if you're looking to get a new remote and don't already have the Pronto. Granted it is a bit pricey and you have to spend the time programming if you want to just point and click to flip between inputs and outputs on the DTC-100 and inputs on the TV.
As for the HD the DTC outputs 1080i on the RGB outputs if fed a 1080i or 720p signal and everything else it outputs at 540p on the RGB. Keep in mind that with the Sony XBR that a 540p signal output by the DTC will force the Sony into 16x9 mode and you can't turn it off on the Sony. Thus a 480p broadcast that is 4x3 is converted to 540p and displayed by the Sony with letterboxing on all sides, thus reducing your picture size.
However, the DTC outputs 480i on the S-Video output for everything. You can switch between S-Video and RGB with one button press on the remote. (Granted you (may) have to switch inputs on your TV). You can not have both RGB out and S-Video out active at the same time on the DTC.
There are a number of aspect ratio settings. You can find more information on them in the DTC-100 manual. The manual can be viewed/downloaded at RCA's website. The manual is in PDF format so you'll need Acrobat Reader to view it...
http://www.rca.com/documents/15407990_1118_25.pdf