Data taken from my heart rate monitor for my last run (5.33km, 12.3 km/h 26mins 3.5sec) tells me my average heart rate for the run was 168, with a max of 179. That's probably an 80-90% work out for me at my current fitness. At the start of the year I managed to get my heart rate over it's theoretical max, but being 35 years old it's not that hard to do lol.
While it's good to know your workout heart rate to make sure you are in the right zone, 2 things that I think are just as important as your workout heart rate are your resting heart rate and how long it takes for you to get back down to a resting rate after your workout. For example my resting heart rate is about 70, and within 5 mins of the end of a run my heart rate has gone from 180ish at the end of the run back down to about 100.