As Bootstrap nears releasing their final version of Bootstrap 3 they will continue to roll out Release Candidates for bug fixing and testing. We have elected to keep as up to date with them as we can under the assumption that release candidates are fairly stable and shouldn't change too much between now and release. Tuesday they released their next release candidate, RC2. You can read about the full changes at their blog but I'm going to highlight a few of the main things that changed for us.
col- to be the default size for all devices. RC2 has removed this default class. Instead they have added a new -xs size for really small phones and a -md, though I think this was in RC1 we just never used it. The best way to do a default size for most devices is now to use to col-sm-. Use the small version because it works for devices with a screen resolution of ≥768px. This is what most modern devices are using. Anything lower than that will default your spans to be like a col-12. If you need to make changes for screens smaller than that use col-xs-.
navbar-header. Change nav-collapse to navbar-collapse.
button-large to button-lg and button-small to button-sm. Form groups is also affected by this change.
Those are some of the main things we found. I'm sure there are plenty of things that are affecting other people. Head over to their blog to read all about it. I'll update this post if I come across anything else.
modal and not the modal-body. To fix this just move all of the divs below the modal into your remote document and that should work for now. It's an issue they are discussing.
EDIT Aug 19 1:01PM
When you print it uses the col-xs tag. Make sure to update accordingly.