Hi
I had IUI with Dr Lang (only one round as it was pointless with my diagnosis)
Anyway yes you get 3 usually on your insurance but it might be best to check with your insurance first
As for medication, he gave me a low dose of clomid (sometimes low dose of Gonal F is used also) - you can certainly ask him about non medicated and he would likely give you the pros and cons answer but ultimately it is your choice i suppose. What reasons do you want to have an unmedicated cycle? they only like you to produce 2 follicles and often IUI cycles are abandoned if they find more than 2 follicles after stimulation.
Success rates - well obviously it works for some but I think IVF is clearly more successful but if you can do IUI (i.e you dont have blocked tubes) then you may as well give the 3 free goes a chance before making any further decisions and who knows you may be successful
Good luck