I've just returned from Toronto with my L-1 extension.

This is what I found out:

• Do not turn up at the consulate with any electronic devices - there is no bag check. Leave phones, laptops etc at home (or the hotel).
• Be prepared to wait. My appointment was at 12pm (midday). I turned up about 10:30am and stood in a line that started on the sidewalk and wound its way into the consulate building ending an hour and a half later with someone pre-screening my documentation. That's right, outside on the sidewalk - check the weather and be prepared. I waited a further hour (seated this time however) before actually having my interview.
• Once my interview was over I was given a ticket and told to return the next day between 3-4pm to pick up my passport. When they say 3-4pm, they mean it. I turned up at 10am but was told to return at 3pm. I collected my passport from a kiosk outside the consulate. Again be prepared to wait. I was toward the front of the queue and it still took 40 minutes to get my passport. I was there in the summer and had a sun hat - I needed it. Winter? Wrap up! Rain, take a brolly.
• My passport and visa were returned the day after my interview. However, this is the minimum turnaround time. For non Canadian residents, like me, they suggest planning for upto 3 days. Canadian residents should plan for 1 day. Maybe I was lucky? Note, these are merely guidelines set by the consulate. There are no guarantees - infinity appears to be a possible timeline.
• Lastly, and obviously, ensure you've prepared all paperwork. Then check the paperwork again. Then get someone else to check the paperwork. Remember, these guys do it for a living - they don't miss a thing.