I used my Blichmann burner this weekend and I have to say, it is pretty awesome. Putting it together was a piece of cake. It's sturdy as hell and the 24" leg extensions keep the kettle at a nice, convenient height.
The burner is super quiet. I could hear it when I was kneeling down near the burner itself, but when I was standing, barely a whisper. Defintely quieter than my last burner which sounded like a jet engine.
It heated 7 gallons strike water up very quickly. With my prior burner, I always milled my grain while waiting for the strike water to get to temp. Usually had plenty of time after milling my grain since the old burner was such a hunk of junk. This past brew day saw me rushing to get the 22 lbs of grain milled as the water was ready before I finished milling.
Can't really speak to how efficient it is with regards to propane usuage, but it is said to sip where some other burners slurp.
The only issue I had this weekend was that the burner was so powerful it had my sight glass violently boiling even though I had the shield under it. Need to figure that out (bigger shield, perhaps).
It's not an inexpensive piece of equipment, but it's definitely a quality burner that I don't see myself replacing any time soon.