Good topic!
I think the Macs Dwight was referring to were all of those Performas and Centras, basically anything between the Quadros and iMacs.
I definitely agree the bare TI-99/4As are not worth much. Now that the machine's technical architecture is well documented and the technical information is available, I would have never bought one in 1980!
Here's one I personally would add - the C64! Before everyone jumps on me, I know that this was many people's first machine, there were lots of games, but I had one in my collection and hated it!
When I was in acquisition mode, I thought I wanted a Tandy CoCo 3. Then it reminded me of the C64. ugh. From that genre, I think the Ataris are the only ones I can stand.
I'd add the Sinclair ZX81. Flaky keyboards and the expansion connector. The one I had in my collection had a flaky power supply. I'm hard pressed to think anyone can spend more that 10 minutes with the thing! I sold mine.
I also agree that the zillion XT, 286, 386, and 486 clones are worthless.
After researching some of the machines mentioned in the "most valuable" thread, I'd have to say that the crossover game console and computers don't do much for me.
I might add any machine where you can't get at least a few pieces of software! When I set out to collect some machines, I at least wanted to get the OS, a programming language, a terminal program, an editor/word processor, and a spreadsheet.
I'm sure to have stirred up some passion on some of these machines!