Overall I would say we like this timer a lot! We got it for our toddler, for whom we CONSTANTLY set a timer (30 second timer! 2 minute timer! 5 minute timer! 10 minute timer!) during transitions which overall is a strategy that really helps her.
This timer has a bunch of benefits: it's super visual for her to see time ticking down even though she can't read numbers yet, the 10 minute max is exactly what we use it for so it makes even a 1 minute timer feel like a meaningful chunk of time, it's colorful and fun, it's exceedingly simple to use.
There are a couple aspects that are just part of the design, but not my favorite design choice for how we use it.
1) There's no way to "lock in" the time -- you can adjust the timer up or down any time including once it's ticking. This is a problem only because it looks/feels like a toy, so once we start a timer we have to keep it in sight but out of reach or she wants to change the time up and down.
2) The timer going off entails beeping twice or so and then stopping on its own. This is generally good enough, but if we've moved to playing somewhere slightly further away (see above for why we can't just keep it on the table or something with us) sometimes I hear it but it doesn't register in her engaged toddler brain immediately and having the option at least to have it keep beeping would give her more of a chance to respond.
Those keep it from being a perfect 5 stars, but on the whole it's a solid product for our exact use case.