Interesting
I wasn't aware of any of these problems with Rainbow. I have a gold 2 speed brand new from 2006 with the foam insulation, and the suction is perfectly fine. I do know what you mean about it not being as strong as other vacuums, but it's still has plenty of airflow for cleaning. I'm sure they will find a way to make it stronger in the future. I think, as of now, they have to limit it or else water will get sucked through the separator (at least that's what I read a long time ago) And the smell, I LOVE the smell.
Regarding a new model. After they introduced this latest model, I too was wondering what else they could do? They have pretty much addressed things people didn't like about it...
You should try using another water filtration vacuum like Sirena or Hyla for a week or two. When you go back to using your rainbow, you'll feel like you're going back to a regular vacuum for quick run through's in terms of cleaning up/storage.
My Sirena just isn't as easy to put together,clean, put away as my rainbow. It takes me twice as long with the Sirena. I quit using it and stored it away. I now use my Rainbow.