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.
5D mk3,16-35 2.8 L II, 24-70 2.8 L II, 24-105 4.0 L IS, 85 1.2 L II, 70-200 2.8 L IS II, 100-400 4.5-5.6 L IS,50 1.4,40 2.8, Sigma 180 3.5 EX macro, Speedlite 600EX-RT & 550 EX