Tell me the good, the bad, and the ugly about umbrella policies!

[Erica Ricketts]

My business partners and I are in the middle of a big transition in our real estate portfolio. I am looking for the best companies for umbrella policies-- multiple properties in multiple states: OH, FL, TN, TX, SD, CA, and OR. 

1) What insurance companies have you used and what did you love or hate about them? 
2) Any specific items that you recommend being added to the policy? 
3) Have you ever had a claim filed against your policy? What was the experience? 

I want, no, NEED better coverage and would love your help!