Based on reviews from several sites, I chose this stair stepper because I wanted the most low-cost, basic, simple, entry-level machine. After a few days, I'd say it fits the bill. While it doesn't have adjustable tension per se, the adjustment of the stair height acts in that capacity. It seems sturdy, although when you are NOT standing on it, be careful to not let it fall forward. The lateral motion is easy to get used to. Not sure if there is a scientific reason for it, but it feels reasonably natural. The counter does what you would expect: time, steps, calories.
I'm overall satisfied but there is a CAVEAT that you won't learn about until you purchase the machine. It's not in the description, and it's not in the reviews at other sites: per the instructions, it can only be used for 15 minutes at a time, with a 30 minute rest period between uses. This is so the hydraulics don't burn out. Admittedly, there's no way I could go for longer than 15 minutes right now, but it's a bit cheesy that this issues isn't prominently mentioned. There are two of us, and we had hoped to use the machine sequentially, but now person #2 has to wait 30 minutes before it can be used again. So, this lowers the functionality score to 4 stars.
On the surprisingly plus side is the assembly. Being made in China, this product was likely to come with the usual gibberish English that makes no sense. But no! The instructions are actually clear and easy to follow, with good labelling and all the parts necessary (also labelled). The company gets 5 stars for clarity.
I will update this review after the machine has been in use to comment on durability and long-term performance.