I suppose my all-time favorite at this point would be Tyros. It's easy to operate, reliable, light in weight, has good sounds and versatile styles.
The important buttons are lighted, and along with the huge display allows you to play in the dark.
It accesses styles and songs from user memory, hard drive or floppy instantly.
My second favorite would be the love/hate relationship I had with the Solton (Ketron) X1.
If only the buttons had been in the right place. . . It had a great "live" sound.
The weaknesses, besides the misplaced fill, variation, start and stop buttons, was the operating system was difficult to learn.
There was zero dealer support in my area, and I worried about reliability, even though I had no problems with it.
Two keyboards that were WAY ahead of their time was the Yamaha PSR8000 and the Technics KN2000. Either could still be used today, despite begin a little antiquated as to storage, speed and size of the styles (two variations).
The 8000 was the first kb I had that let me eliminate the vocal harmonizer, outboard mixer, etc. I could still use it today and not be that handicapped.
The Korg PA80 was another kb I both loved and hated. The size and weight was right. The sounds were wonderful. I liked in particular the harmonica and acoustic guitar. I liked the way the organ rotor was assigned to the Joystick. The styles were great except that there were virtually no CW styles, but the fills, intros and endings left a lot (everything maybe) to be desired.
The midi playback was particularly strong, although I don't use much anyway.
Also, the on-board vocal harmonizer was useless to me. There was only one pedal input besides the dedicated volume (or was it sustain?).
I didn't like the OS on it either, but then it is easy to be spoiled by Yamaha's OS.
Of all the others I've had, the Technics KN5000 was pretty good, and the Yamaha 2000 and 2100 were also good, although not in comparison to the Tyros.
I'm looking forward to seeing the next offering from Ketron (if that ever happens). They seem to understand that some of us don't want to lug around 50+ pounds of kb.
My least favorite was the Roland G800. I didn't like the heavy weighted keys. Made my fingers hurt. Physically, it kept breaking. The Joy stick spring broke after two weeks, the buttons began sticking after a couple of months. It weighed something short of a half-ton. The registrations wouldn't remember key transpose (at the time at least). The OS required going through many menus, and the display was smaller than the one on my wrist watch.
It DID sound great though, and had some neat features like assigning two sounds to the right hand and setting the volume pedal to increase one and decrease the other as you pushed it down. It also had some interesting key-split options. I enjoyed using the Joystick when it worked. I think I prefer the joystick to wheels. The G800 was also had one of the first sequencers (as far as I know) to record directly in GM (or GS) format. The Technics had to be converted as did the earlier Yamahas.
Wow, that was longer than I expected.
DonM