Yes I've used it. I found problems with the following. Don't take this offensively, just giving you some insight into what I found not user friendly.
1) I think you should rename "volume" to position size or something that signifies contract/shares. volume means something else to most people.
2 )I think you should restrict the zooming in or out of the graph.
3) I think you should make the profit/loss side numbers bigger
4) maybe colour code the profit areas?
Don't worry, it's ok. It took a bit long for me to respond, sorry about that. I've thought about your hints and here are my conclusions:
1) ok, does "quantity" sound good? if it does, i have some good news) already changed that
2) it was the main feature i needed when decided to create this tool) and it still is for me
3) probably yes, i'll do that soon
4) surprising idea.. haven't actually seen that before. it probably has some advantages, but they don't match the amount of efforts for now.
Thanks for your feedback, it really helps.