I rarely need to wear dress shoes (lab footwear usually consists of clogs/birks/merrels/chacos), but I usually just wear Dansko/Sanita clogs if I'm going slacks-dressy. If I'm skirt-/dress- dressy, I've been known to wear nice flip flops or some other kind of flat sandals depending on how formal the occasion is (or the clogs, if it's winter and heavy-tights weather, I think that looks ok). I have a number of pairs of good ~4" heels that I enjoy wearing, but if I'm out with the BF I'll usually go for flats since we're the same height.