Quantize usually has both a strength value and rate value. One will usually define how big the threshold value (of being off beat) will be before quantization will kick in and 'fix' the timing. The other will define how 'losely' or 'tight' it will fix the timing.

Basically a strength factor makes it possible to have a quantized beat that sounds a whole lot more natural and less robotic.

I'll admit it's difficult to explain though. The MV8800 / MV8000 both have a strength and rate value for quantize. Works great for getting a really really natural feeling.

Someone can be lagging behind in timing, but still be on time because he's the same amount behind with each note. That kind of naturalness is what I'm talking about here. Pretty useful, unless you can get this natural groove going without any quantize (aka your timing is 10x better than mine).