Further update on my Philips 3576 saga --
Returned my 3576 to Sam's Club for a replacement. The stock was lower, but they still had plenty. Picked up another with a May 19, 2008 build date. No more recent date was available.
After I hooked it up to my system (Comcast extended analog; coax to 3576, to signal amp, to 2-way splitter, to TV -- 1st output, to remaining components -- 2nd output; 3576 to TV via component) I scanned for available analog and digital channels.
Good news -- all the available digital channels were available by surfing. I did not do a Wajo stress test -- rapid surfing; I will try that later.
Since I had no previous problems with analog channels, I did not check them.
I decided to do a quick check of recording digital channels, so I set up eight 5-min timer recordings from 8 different digital channels. More later...
One interesting thing I noted when I did the skip-1,2,3 check on firmware versions, etc., was that all the versions were the same as my first 3576 except for one -- the DTV-S Version was DIFFERENT!! -- 0x93 for this recorder, and 0x90 for the first recorder. I don't know if this difference is significant, but so far the digital channels are OK on my replacement 3576 (knock on wood).
Another update after I check the timer recordings.