I've used a Mosley TA-53M with very good results for eight years. Boom is 14 feet long. Would have to take down three large trees at a cost of $1500 to use something with a longer boom. Operationally it's quite good; do pretty well in phone pileups with about 90W. It's well constructed; fair amount of icing at my QTH (Boston, Mass); no problem. A 50 lb tree limb fell on it during a winter storm and bent the reflector a bit, but it stayed up; it's quite durable. Gain is probably near what they quote as is F/B. Some complain about the F/B, but my sense is that this is a compromise necessitated by the short boom.
Mosley can be a bit brusque over the phone in my experience, but that doesn't affect the gear. See:http://www.mosley-electronics.com/amateur.htm
I've heard good things re Tennadyne, but have never used.