That depends on what you want to do with it. That heater is plenty large enough to dramatically extend the pool season. If you are starting from very cold water and want to be swimming right away, that heater will take a while to get the pool up to temperature, and a larger heater will give a better experience. That heater is also not large enough to allow you to swim reliably in the middle of January.
My heater is just a little larger than that and my pool is much larger. In the early spring my heater can take several days to a week to get the pool up to temperature. Once the water is warm, it keeps up just fine.