Do hedgehogs get on with other pets?
This will depend a lot on the characteristics of the other pets in the house and your hedgehog. As well, any interaction between your hedgehog and other household pets should be carefully supervised, especially in the beginning. But generally speaking, hedgehogs are pretty well-equipped to defend themselves from other pets and seem to tolerate other pets quite well.
Cats typically seem to quickly develop a healthy respect for the quills of a hedgehog, and keep a respectful distance. Dogs, too, are generally quite wary of the hedgehog's armor, though care must be taken with large, boisterous, or highly prey-driven dogs, who could quickly injure a hedgehog with rough play despite the quills. As for other pets, they seem to get along fairly well with hedgehogs as well.
Ferrets might be a bit trickier and more persistent at trying to get at a hedgehog, but chances are they would quickly come to respect the quills, too. Other small pets are usually not a problem, either. If your hedgehog seems stressed by encounters with any other pets (such as urinating or defecating in fear), then your should restrict contact with the other pets. Also, you should not let other pets harass your hedgehog when it is in its cage. Introductions should be made carefully, preferably with you holding the hedgehog.
Overall, hedgehogs are quite amiable and non-aggressive, which combined with their excellent defense mechanism, makes them a fairly agreeable combination with other pets.
From personal experience, one potential downfall of hedgehogs might be fearlessness. My hedgehog pretty much ruled the roost despite the fact that 4 large dogs shared our home with her -- but our dogs were pretty laid back When she was in her cage, the dogs ignored her. When she was out, she would fearlessly march up to our big German shepherd and snuffle around in his fur; for the most part the shepherd seemed wary (perhaps even afraid) of this little spiked creature. Perhaps not all hedgehogs are like this, but she seemed quite fearless, so caution would definitely be warranted around animals with a strong prey drive as your hedgehog might not be defensive enough around them.