I am using Angular.js for an application that uses hidden trs to simulate a sliding out effect by showing the tr and sliding down the div in the td below. This process worke
Using ng-repeat on tbody appears to be valid see this post.
Also a quick test through an html validator allowed multiple tbody elements in the same table.
Update: As of at least Angular 1.2 there is an ng-repeat-start and ng-repeat-end to allow repeating a series of elements. See the documentation for more information and thanks to @Onite for the comment!