I have used Rainbow for 13 yrs. Although it was expensive ($15000 at the time that I bought), it functions good for these years, especially if you have pets at home.
I had dogs and they stayed home. Before I bought Rainbow, I had to buy a new vaccumn cleaner every 2 to 3 yrs even the vaccumn cleaner still worked, because you could find the smell of pets or bad smell every time when we used it for a couple years. That was the reason why I bought it even it was expensive.
My rainbow is still good, never has mehcanicial problem, but only need to change some of the accessories.
Anyway, after 13yrs of usage, I have to replace one of the plastic pipes. If there is any sales here, please PM me. I could not search the company to make an order.
I am using my rainbow for over 3 years also. very good and powerful. thought the look is a bit so so (very bulky and like a robot). but i did help me for my allergy (basically 90% recovered) and also filter the pet's hair.
I think rainbow is good but still it's a bit overpriced.
if u don't have nose allergy/pet, u should pick other less expensive brand.