I am using a Sigma 180 f/3.5 EX. To be honest, I use it very unfrequently, but I do like the build quality and the IQ. One of the advantages of a longer macro lens is a slightly longer working distance.
Below a shot I took today of a flower in my living room.
EOS 30D; f/3.5; 1/125; ISO 100; natural light; -1/3 EV; Gitzo tripod; no post-processing, just slight crop.
5D3, 16-35LII, 24-70 2.8LII, 24-105L, 85LII, 70-200 2.8LII, 100L, 135L, 100-400L, 50 1.4, 40 2.8, Sigma 180 3.5 EX, 1.4x TC III, 600EX, 550EX