I used to have one. It is a decent cardio workout, but there is no resistance adjustment. It's also pretty loud if you are working hard. The cranks are quite short. They are very well-built, but if you get a used one make sure the chain tension is properly adjusted - it's a little finicky.
Since I'm not a fan of indoor exercise I got rid of it.

-F

 

Good workout but super loud and nearly impossible to make it a regular habit. 99% of them end up being a dusty coat rack in some dark corner.

A Kickr combined with a Zwift account is much more engaging and it's way more likely that you'll actually use it.

 

Those things are made for older/sedentary people. They have no resistance adjustment so you can’t really do any proper interval training on them.

 

lol.... thats why they are one of the most used pieces of equipment in crossfit gyms?

I wouldn't suggest it in place of riding a bike, however I have one and have used it for intense sprints... nothing quite gasses you like those do.

Edit - Funny enough, I have an extra one in pieces (in the middle of a rebuilt/refurbishment) and I was trying to figure out a way to link it to a mtb frame. The fan/wheel with cage is about the size of a 29" mtb wheel. I would love to be able to hop on a mtb platform and crank out miles on it instead of the traditional positioning/arm use

 

I ran into Q-factor issues due to how far apart the pedals can be on these and had some knee pain. (Significantly wider than a fatbike.) No issues on a normal sized trainer/spin bike.

 

How about an elliptical?

 

The Airdyne is a good machine in terms of energy systems. You won’t necessarily build much strength with it though. The Airdyne bikes we have at my cf gym have resistance . The modern Airdyes all have resistance control and have a monitor with screen to track distance, time and calories burned etc. We use them mainly for HIIT workouts. Although you pedal, it is not the same as a bike. If you are looking for a cardio machine for a homegym, is SkiErg and Rowers are another option. Personally I like running instead of AirDyne/SkiErg/Rower/Treadmill but it's nice to mix it up.