A word about Roombas and pet hair:
Our home has one cat, one constantly shedding 12lb rabbit, and most devastating of all to our monthly lint-roller bill - a siberian huskey. When our vaccuum was broken for a week, there were literally tumbleweeds of fur drifting across the open plains of our living room. So, I bought this Roomba.
What I've found over the past week is that the Roomba is EXCELLENT at defeating hair demons. The key is patience. That little guy's bin is so small that it literally fills up after traveling a total of about 15 feet. However, once I discovered that he needs his diaper changed every 90 seconds, I realized that (judging by the total amount of hair in the trash) he was actually more effective than the regular vaccuum that came before him.
My point is that for huge pet hair jobs, an ideal situation would be a serous cleaning session (about 5 runs with a Dyson), and then to run the Roomba at least once a day after that.
Additionally, one of the Roomba's weaknesses seems to be why it is so successful: Those wild brushes. After every third emptying, the brushes need to be relieved of the fur-ropes that form around them. However, it does seem like those brushes are grabbing the long hairs that a lot of vaccuums skip over, and I've never in three years cleaned the brushes on my old vaccuum. Just something to think about.