What you want to do for an upshift is load the petal with some pressure, rev to the shift range, and then partially close the throttle. The transmission will jump into the next gear. You can use it to go down too but it happens around 2500rpm so it's pretty much useless. I am no expert but what I've heard is that it's fine for the transmission if done correctly.
I do it sometimes from 1st to 2nd and it works well you just have to follow through. Never had an issue, actually. I've always found the hardest is trying to put the right amount of pressure once you are up past highway speeds, sometimes I feel like I might have forced it into 4th/5th/6th but the 9er never complains.
Just keep in mind you are still putting metal on metal until those shift dogs slip into place every time you do a clutchless upshift. Don't get me wrong I do it too except between 1st & 2nd, but it does accelerate some wear on your transmission instead of the clutch plates which are designed to wear for routine maintenance.
My buddy who is an avid dirbiker and street ride like myself does pretty much all clutchless shifting outside of 1st to second.... both his bikes are in need of new transmission due to gears popping out etc.
My bikes on the other hand have zero issues and the clutches arnt even close to needing to be replaced even though every shift i do uses the clutch.
and all of our bikes have right around the same miles / hours on em.
Unless you are track riding and have a quick shifter.... save yourself the hassle and use the clutch.
Just started clutchless shifting myself higher revs shift better- Clutch in from 1st to 2nd then Clutchless all the way up and Clutch all the way back down. I have felt like I forced a gear or two into place (4th mostly) I would be curious to see what technique everyone uses on the 9er, dont want my transmission failing in a few thousand miles.
I started clutchless shifting because it seems to be silky smooth when you do it right and prevents pillion head bash
Even with poor technique it would take a lot more than a few thousand miles for any noticeable detriment to the transmission. The sequential gearbox is designed for such use. It is simply a matter of if you want to take the absolute best care of your bike and prolong the life of the mechanical parts then you will use the clutch. If some premature wear and tear and slightly shortened lifespan of those mechanical components is ok with you then clutchless upshifting is the way to go.
For example I have a Dynojet quickshifter installed on my old 1000RR trackbike and a Bazzaz QS installed in my new ZX-10R racebike and I beat on both of them like they owe me money. I expect them to fail at some point if I don't wad them up beyond all recognition first.
On my pristine vintage 1977 RD400 and 88 VTR250 both of which it is very difficult to get replacement parts for I always use the clutch without fail.
So to sum up what i'm reading...
If someone is looking to buy a used bike, that has maybe 20,000 miles or more, and they learn the P.O. was an advocate of clutch-less shifting, the buyer should walk away unless he is interested in rebuilding the transmission (and replacing the gearing).
Sounds like not a good practice for an everyday rider.
A race bike is different - no question.
Let the buyer beware!