Mostly TNT, TBS and A&E. Discovery has done it from time to time but not too bad.
A&E does a standard stretch, not "FlexView"
I've never seen Discovery stretch. They generally do a partial zoom. They don't quite zoom all the way to the edges of the screen- you will see thin black bars on the side, but they also chop the top and bottom edges off.
Technically speaking, this is even worse than stretching or "FlexView", because they are actually REMOVING part of the picture. But personally, I don't mind as much, because the picture is not actually distorted, just trimmed. I often don't notice the difference for a while. Any kind of stretching is obvious the second you turn to it.
HGTV/Food are the only channels that seem to be using FlexView these days.
In my opinion, here are the different ways to handle 4:3 programming in HD, from worst to best.
-"FlexView"/"Stretch-O-Vision"/"Panoramic" (HGTV/Food)
Destoys the picture- cannot be corrected at the viewers end.
- Any kind of zoom (Discovery channels)
Removes part of the picture permanently...however, does not distort the picture. Generally looks pretty good.
-Standard stretch/PAR change (Turner/A&E channels)
Distorts picture, but can usually be "undistorted" by most TVs.
-Logo bars (ESPN and most other sports channels/Hallmark Movies)
Leaves picture as is, but adds distracting logos.
-Pillarbox (ABC/Disney & NBC/Universal channels)
Leaves everything as is. Viewer has the choice to stretch it themselves, or view undistorted.