This is a rather interesting find by kav in the CrackBerry forums. Previously any OS you installed on AT&T BlackBerry Bolds never "unlocked" the network selection mode option on those devices, but with the release of 184.108.40.2062 on CSL that option is now available to all AT&T Bold owners.
Some of you may be asking why this is so important. Well, for those who may be in a not so hot area for 3G can now set their device to a 2G setting in turn saving your battery life, allowing better call quality and having applications even run better. Having your device working in an area that has weak 3G causes the device to constantly be searching for a better 3G signal even though it may never find it when their is a perfectly fine 2G signal that it could attach too. In short, it causes less stress on your device, it's a good option to have.