After much heart aching and research I have finally taken the plunge with an upgrade for my cheapo Canon 50mm f1.8. The options were Canon 50mm 1.4, Canon f1.2 (no, not really an option at that price.... ) or the Sigma 50mm f1.4
The consensus view on the Sigma seemed to be 'fantastic lens, if you get a good copy with no focusing issues'.
I bought the Sigma, my first non-Canon lens, and a big deal considering my L-itis.
What swayed me was 1) a great price from a local walk in store 2) a 7 day no questions return policy 3) the offer from the store for free calibration to my 5D MkII if needed 4) a 2 year guarantee from Sigma. And 5), off overseas soon, so 10% back from the ATO
I used this calibration test when I got it home, and it seems to be spot on so far. Attached a test shot, at f1.4, auto focus on 'manually focusing'
Fingers crossed, now to try it out on some real subjects....