I have two of the G-series Kirby vacuums, a G3 Model and a G5 Model. The Sentrina is an improved version of the G-series.
The G5 is something that I bought used for $750 15 years ago and it still works great. I had a string of plastic vacuum cleaners before this, so I am hesitant to get another plastic one like the Dyson. I don't like the bag-less cleaners either. The Kirby bags are cheap and effective.
I bought the G3 just last year for only $30 and restored it to brand new. The parts are real easy to find on EBay. All it really needed was a Lexon Fan, but I felt like making it brand new. I took it apart, sanded down the scratches on the aluminum. Using a buffing wheel and jewelry polish rouge, I buffed the aluminum to a mirror finish. New wheels, New cloth bag, New Cord, New Belt, New Lexon Fan, New Handle Spring, New Light Bulb, New Light Lens and New Rubber Bumper. Yes, I unnecessarily tossed an extra $200 worth of nice parts on it, but I wanted to bring it back to new. That was a fun and rewarding workshop project:)
You'd be surprised at how cheaply you can get a Kirby from Craigslist. There is usually someone who will unload their perfectly good Kirby for $25 because the beater brush stopped working because they didn't know to change the belt when you do the third bag change.
Kirby's marketing isn't as slick as Dyson. Brand New Kirby's retail for $1,800 the last time I looked (you'd be crazy to buy a new one).
Kirby's are heavier, and have a retro look, but they Do Work Real Well.
The $30 G3 that I bought for the motorhome is a little overkill for what I need, but the attachments are nice to use for the little things around the motorhome. You could inflate an air mattress, remove the dirt from the Fantastic Fan screen or store a bunch of pillows in a Space Bag using the hose for suction. I once used it to pressurize a kitchen cabinet so that I could go up on the roof with some soapy water to locate a leak.
Go Kirby!