Like I said, it all adds up. After a handful of upgrades and part swaps I managed to drop about two pounds off my stock Epic Expert 29er. It sits in at just above 23 pounds. Some of the major weight savings came from going tubeless, switching over to the SRAM XX cassette, carbon post, carbon bar, and carbon-railed saddle.
Upgrading your bike can be an expensive hobby, but you learn and appreciate the details about your ride, fine-tuning every last bit so it fits to you and your riding style. Two pounds may not sound like much, but you definitely feel it when accelerating and climbing, especially if it's rotational weight.