are king springs any good?

I don't know if it's reasonable to give a simple yes or no answer, but I can say that I used to have King springs on stock struts, and the ride quality was terrible, body-jarring. I would almost hit my head on the roof if I went over a speed bump a bit too fast.

short answer: No (yes I've had them before).
maybe ok for a commo

Also the fact that we have MacGayson ****s all round it rides harsher than double wishbone. My mate has a 318is with Kings super lows which is probably too low and quite stiff for me but he seems to think it just manageable. Excellent road holding most likely thanks to the Blisteins on that car.
I may/may not have a set of late model (Rev 2+) OEM springs for sale soon if you're interested (never put them on)...these are 17mm lower according to Reddtarga and ride quite comfy with Konis.

I would go to a reputable suspension place and have a chat to them, preferably one that deals with the mr2 if you want to get it handling well the way you like.
 
More or less, springs are springs, they have a certain spring rate and springs with the same spring rate will behave the same regardless manufacturer.
 
Then there is the shocks which need to be matched well with your springs, and the shocks have a huge impact on ride quality.
 
I have been in an mr2 with lowered springs and konis, and the ride was much more comfortable than my stock mr2, and less rolly around the corners etc.  I was amazed.
 
Cheers
 

springs are not springs if they sag at different rates on each corner i.e. King
+1 to getting good shocks though!

I had them in mine also and like others have already pointed out the shock needs to be mated to the spring. I have two sets for sale alot cheaper than the ebay sale if you are interested still.

How do the Kings compare to TRD springs?
Also anyone know what the height difference is?
 
I had KYB excel-G inserts with King springs, and intend on getting Koni adjustables inserts with TRD springs to replace them. The kings are too jarring on NSW roads. I already have the Koni inserts, but maybe I should try them with the Kings first before getting the TRD springs. I would prefer not having to go through the hassle of changing over suspension twice though.