Heres the issue - when Im going betweeen 40 & 48 mph, I will slightly step on the gas and it feels like the transmission is slipping. Push the gas down a little more, it downshifts and everything is ok. Only happens in that speed bracket and when ithe gearshift is in D.

Just changed the trans fluid & filters (and cleaned the magnets), still happens. But the shifts feel firmer and it downshifts quicker.

Any suggestions or am I just going crazy? Anything other than another $1600 tranny rebuild (had to get one on the 84 deville).

All of the 90's transmissions had electric solenoids on them for shifting. The early ones especially had problems with bad grounds to the solenoids. I don't think with the problem you describe that it is serious. I would get a transmission place to check it out. If you don't like the answer, check with another one. I've found a couple of answers to the question usually leads to the solution.

My 2 cents

I had a Cadillac dealer run some diagnostics, and it turns out the transmission is fine - one of my coil packs is going bad, and the ICM is going with it (also causing stalling at idle), causing misfiring.

Allot easier to work on that than a transmission.