One new feature added to surfaces for 2013 is the ability to specify a maximum angle between surface triangle lines. This is supposed to build surfaces more intelligently by removing triangles that exceed the maximum angle and result in less erroneous triangulation.
See the following link for more info:
This is intended to be applied to triangles that make up the outer boundary of your surface only. However, after creating a surface (style - Border Only) from some LiDAR data last week I noticed there were 'holes' in the surface. See below:
After some searching I checked the max angle and set this to 'No' and rebuilt the surface and the holes disappeared.
So it would appear that the setting is applied to internal triangles also. (which it shouldn't be according to the help menu)