Before you buy check and compare specifications!
I have the hand held Makita 4 stroke blower and it is a very good unit. I had a look at the backpack model and compared the air volume and speed to the Shindaiwa C4 blower and the Shindaiwa C4 would literally blow it away.
Makita BBX 7600 air speed = 313 kph air volume= 14.1m3/minute
Shindaiwa C4 air speed = 360kph air volume= 26.95m3/minute
(specs sourced from sales brochures)
The Shindaiwa has nearly double the air volume and air volume is more important than air speed.
I concluded that it wouldn't be worth getting. The main reason for getting a backpack is that you have more power than a hand held and the Makita just doesn't have enough. The hand held Makita puts out 10.1m3/minute so the backpack only has 4 more cubic metres. Apparently the Stihl BG 600 has even more power than the Shindaiwa C4.