I've run lots of mis-matched sets of tires on my 02 zx-12. I currently have 55,000 miles on it. I commute daily. So my primary issue is rear tire wear in the center. Plus with the power of the 12 wears the rears as well. On my commute I have a few twisties I use for a bit of fun and keep my cornering skills sharp. I run the fronts and rears to the edges so I have some skills.
If money were not an issue I'd run matched sets of soft tires all the time and have them replaced as needed in pairs. On the track it is essential. In the real world money is an issue, so I run the combo that suits me the best.
That being said here is my tire experience. I always run a softer front. After the junk stock dunlops wore out. I ran a Bridgestone BT10 front and BT10 rear. These felt good together, but the rear tire wear was lousy.
I replaced the rear with an Avon AV46 rear. The avon wore really well, and the grip was not to bad, but could be better. The BT10 and AV46 combo was not to bad.
I then ran a BT14 front. This tire had more grip than the BT10, but it had a lot of cupping as it wore out. I continued to run the AV46, this combo worked better with a 190 rear, then the 200 rear. Better turn in that matched the BT14. I still wanted more rear tire grip.
Michelin had come out with the pilot powers. And I was hearing rave reviews about them. So I put a set of them on. Yes they are very good tires. They have lots of grip. But the rear wore out very quickly.
I needed a longer wearing rear. I heard the new Pilot Road 2's were coming out. So I waited. When they did they had a 240 dollar price tag. Very expensive. The Bridgestone BT21 is also a dual compound tire and at 140 dollars was reasonably priced. So far I like it, it has good grip in the corners, and seems to be wearing well. I'm not so sure how well it matches with the Pilot power front. I'll probably try a BT14 front when the Michelin wears out. we will see if the combo is better, and if the 14 still cups.
I will be replacing the tires on my Son's 00 sv650. I am leaning to a set of Pilot powers front and rear.