Go for it Evil Pixie, it's a must for anyone in geek land. I'm another HRM fan.
In addition to reading the thread on HR, you could spend time just gathering the data from your HRM. All the formulae in the world are only relevant when set into context of your individual HR at your existing level of fitness.
Don't know if you keep a training log but if you don't start now and note the length of your runs, distance if you know it, and av HR. Over time you'll build up a good picture of how your HR behaves in relation to your running. Also you'll get the satisfaction on seeing improvements in your fitness reflected in your HR.
Good luck