I have the $13 scope from Radio Shack. It works but takes a while to get good at it. You really have to make sure you are not confusing shadows with brown/amber trichs. My neighbor bought a $30 dollar handheld that works much better. I will have one of those next year since it is really easy to use in the field.

I am definitely looking for a better model like the ones shown above. It would be really nice to have a view on my PC. I have a laptop that I could take into the field but I don't think the scope will run on batteries. I am off the grid so have to use generators for electrical power.