So I bought it and tried it out. My reasoning is that it'll be easier to keep on top of a cup than constantly buying and then forgetting to bring tampons. To that end, it was a success.
However, these things really are just like a tampon. Since I got my IUD, I've had to buy those "ultra-super, explosion of cotton in your vagina" type tampons and for some reason, I thought it'd be fine to buy the normal size of the cup. On my heavier day I was running to the bathroom every hour. Everyone who said this thing is a bitch when it over-fills was spot on.
According to one of the websites about it, there's a much larger cup that women with heavier flows go for. I bought that and will have to wait a month to see if it works better.