Again, I have no experience with NASDAQ regarding getting out of a stock. I would assume it would be instantaneous if you submit an order outside the market.
Under normal conditions at the NYSE, I load and submit a price about 5 cents worse for me and I usually get a filled at or around the price I need to get out. The fill takes about 5-10 seconds. It sometimes gets hairy during fast market conditions wherein the specialist is processing a huge amount of orders-usually around major points (round figures, support/resistance/cleanup points).
Around those points I know specialist will be busy so I enter a market and hope for the best. Ex XYZ is 99.95/100.00. If I am short and it starts printing 100.00 I cover short at market-I might get filled at 100.10 or sometimes 99.90 because the next order in the queue of the DOT is a big sell order. Of course that only happens 10-20% of the time but I'll take it. Just remember this "delay" vs. NASDAQ is a double edged sword. Sometimes you want to buy something and the SP turns over, giving you the chance to cancel the order.
Bottom line. The pros and cons of NYSE execution, (while admittedly slower by 2-10 seconds over NASDAQ ) tend to cancel each other out given a huge amount of sample size ( I trade between 70-100 times a day) which means that trend identification, money management and discipline will be, at the end of the day,month, year, career will be the main determinant of your success.
Hope this helps.