I've been keeping Lucky Bamboo in tanks for several years (though not submerged). Fry love the root balls. I also did a little experiement with two 29 Gal tanks stocked, filtered, the exact same way. The tank with bamboo (only 5 stalks, in the HOB filter) had slightly lower nitrates than the one without.
I've tried keeping it fully submerged as well as left a few that fell over. Every stalk I've ever had fully submerged died shortly after. I've had them last different amounts of time but none lasted (submerged) more than a month, most around a week.
I've heard other people say otherwise, but I suspect they just didn't wait long enough.