Just for those interested, here's Lenstip's review on the Sigma 18-35mm F1.8 lens. Fascinating lens.
http://www.lenstip.com/374.1-Lens_review-Sigma_A_18-35_mm_f_1.8_DC_HSM__Introduction.html
http://www.lenstip.com/374.1-Lens_review-Sigma_A_18-35_mm_f_1.8_DC_HSM__Introduction.html