@billybud21 . . .
Rainbows are decent performers but -- again -- an acquired taste. The big issue is whether or not users are prepared to give them adequate care. They certainly are not worth the investment if the user only does slapdash maintenance.
A long while back I read in some of its historical material online that the use of water actually came about more by accident than on purpose. However, once it was found to work it's inventor forged ahead.
Back in the early days it appeared us men folk had assumed that all-day homemakers -- quite the usual occupation for women then -- had time for everything. Thus there was presumed to be no problem with the five extra minutes it took to set up and the fifteen minutes or so it takes to dump the water pan and to wash and dry both it and the separator.
Even vacuums with shake-out bags, which was basically all there was, were considered the easier deal by many. Yet compared to current bagless machines the work for maintaining a modern Rainbow may be more or less the same in my opinion.
I've had bagless machines that I liked a lot but couldn't stand to see sitting dirty. Depending on who you are, looking at those clear collection bins cuts both ways. You find yourself not always thinking of how much you picked up but what the glorious machine you bought looks like when its innards are grungy after just a few uses. Thus, I got to be regular about washing filters and collection bins.
Cumulatively, the time spent to clean a bagless machine's bin and filters plus down time for drying if you don't have extra filters on hand adds up to time spent for several after-use clean ups of a Rainbow.
If you're a person who doesn't mind the time involvement for keeping and using what's actually a display of great science and if you're also a little on the fussy side, Rainbow should not prove a problem. If you're someone who's on the fly a lot it will present problems. You can't just yank one out of the closet and toss it back in -- not if you want to keep it.