I'm having the same thoughts about kicking the season off early, but I'm waiting for two reasons:
- I don't have transplants started and ready to plant out yet. I'm not starting anything like tomatoes or peppers early because of the risk of frost if things return to "normal" for a week in mid-May. I'm not sure I'd have enough row cover to protect everything.
- The ground is still very cold. I stuck a soil thermometer in my garden a couple of days ago and while everything has melted, there may still be chunks of frost a few inches down (i.e. completely frozen ground) and the soil temps at the surface are only about 50°F. Not much will germinate at this temp, and even plants that will germinate will do so very slowly.
I will, however, probably plant out hardy plants a couple of weeks earlier than usual, assuming the soil warms up early. For example: onions, spinach, peas, and kale. (Probably transplants of the spinach and kale, just so that they germinate quickly inside and then I'll transplant them small.)
If you have a packet of seed for, say, lettuce or spinach, and you're never going to use up the whole packet, you might as well plant some out and see what happens. If the weather stays this warm, you'll have early salads. And even if it gets cold again (or snows in April!), it probably won't hurt the hardy stuff much anyway.