Sometimes, yes, but I've found "too-practiced" talks to be a bit off-putting as an audience member, especially if it's supposed to be more academic subject material. Probably not an issue if you're giving a TED talk, or you're doing a product rollout, but if I'm listening to a computer-science talk, and it's going to err in one direction or another, I'd rather have the not-that-rehearsed talk that fumbles a bit, versus the perfectly-scripted one that feels more like I'm watching a performance than listening to a scientist give me information.