It's marginally faster than a .308 and the .270 WSM beats it handily.
I'd rather have the speed than the weight.
If I thought I needed something with more umph for elk, then I'd probably go with the 7WSM or the .338 RUM, which puts a more appropriate amount of speed behind that lumbering slug.
Yes, it's somewhat popular in the AR-10, but I suspect the .308 will reign supreme in that category for a very long time.
As for other semi-autos, I don't see Browning clamoring to make one either.