You will run into problems with worldspawn geometry, since the engines are usually working with single-precision floats. You'll not be able to distinguish anymore from planes that are 0.5 units apart (which sounds ok, but for angled intersections and sealing geometry this might not cut it, literally).
(This question really is not so much about the editor, which is working with doubles to store geometry - even though the DR renderer is also operating on single precision floats - this provides a huge performance benefit over doubles).