To be honest, no. Even the sweetish Belching Beaver milk stout couldn't come close to matching all that ice cream sweetness (my wife had the peanut butter version), nor did it have enough fizz. It was more a case of novelty awesomeness (and it was hot day and we were sitting in the window, so ice cream in some format was called for, and well, we were in a bar, so needs must). I won't be spooning ice cream into my stouts on a regular basis. Unless it's Guinness, in which case chuck away the original contents of the glass and replace with ice cream.
For a proper ice cream float you need something sweet and fizzy like cola so you basically end up with fizzy ice cream. Birch, sarsaparilla, and root beer floats (with vanilla ice cream) are an American staple and quite nom. Normal beer, not so.