I've had this airdyne for over a month now and I've been using it for HIIT (20 seconds all-out intensity 10 seconds rest) and it hasn't disappointed me at all. First of all, this airdyne arrived in great condition, it was easy to assemble as the instructions are very easy to understand and there isn't much parts to assemble the airdyne. When I first got on the airdyne to do my intervals, I was gasping for air within the first 5 minutes and my thighs felt like they were going to explode. The resistance the fan offers is tough and I guarantee that your quads will feel like mince meat the next day. As far as the airdyne goes, it is very sturdy as it doesn't wobble around when you're on it and it also has adjustable feet for uneven surfaces. The parts are very sturdy and versatile and I have inspected the belt and bearings multiple times after use with no signs of extreme wear. Personally, I didn't think this airdyne was up to the task of HIIT, but I was wrong which makes this airdyne ideal if you are on a budget.
This airdyne is superb when it comes to increasing your fitness level and it is a good addition to my garage gym. The fan is quiet, however it is not as quiet as the AD6 or AD8. It sounds loud when you're on it but when someone else is on it, it sounds like a Dyson tower fan which is very silent. I am very happy with this purchase and it is excellent for the price. I think that it will last me many years!
My experience in using this bike started off as being an amazing piece of equipment. But then about 3 months back the internal flywheel and peddles shifted and actually ground through the external casing forcing me to stop using this extremely useless piece of equipment. I have another exercise bike which I've had to revert back to and has been a total workhorse compared to the AD2 Airdyne bike. I bought this on recommendation and wish I'd invested my money elsewhere.