In general, a robot vacuum will do a good job cleaning hard floors when running on a daily cleaning cycle. They are less efficient at cleaning in corners or along walls, so you will still need to clean these areas yourself even if your house mostly has hard flooring.
Robot vacuums can also clean on carpet, although their small size does not provide them with a lot of suction power. Even if the carpet looks clean, the lower suction power will probably only achieve a surface clean rather than a deeper clean. Over time, this can damage a carpet or rug, so much sure you still give your carpets and rugs a good clean with a barrel, stick or upright vacuum cleaner from time to time.
If you have pets around the house, some robot vacuums are great for cleaning up cat and dog fur. Of course, just because your robot vacuum can handle pet fur, does not mean that your pets will get along with it, so it may be worth testing it with them before leaving your robot vac and pets unsupervised together.