The main highlight of Wine 1.3.27 is presenting support for multi-sampling in Direct3D. But besides Direct3D multi-sampling there is also a new version of the Mozilla Gecko engine for rendering, improvements to the network proxy handling, better write support for MSXML, side-by-side manifests for built-in libraries, and various bug fixes.
Multi-sampling is one of the anti-aliasing modes supported by Microsoft's Direct3D that up to this point has not been supported by the Wine implementation. With Wine 1.3.27+, it should begin to work for games that support the rendering feature to improve image quality at the cost of performance.
Read more about the Wine 1.3.27 changes in the WineHQ.org announcement.