Image quality (ISO 12233 resolution chart crops), vignetting and distortion results along with eye candy are now available on the Sigma 180mm f/2.8 EX DG OS HSM Macro Lens Review page.
I'm not certain if or when I will get time to complete a full review of this lens, but hopefully the test results will provide the information you need to know.
Update: Under the first clear day we've seen in several weeks, flare tests results have been captured and are also now available.