I'll add my 2 cents.
Had nothing but positive experiences w/ AwardWallet's booking service (their name is escaping me right now...think it's called Book Your Award).
Easy to work with and down to earth. I'm 3 for 4 with them (the 4th they literally couldn't find a TPAC in biz without including a 12-24 hour layover in Seoul or NRT...probably Delta's fault though!)
I will say this: with so many new companies popping up, I'm not sure how long they can justify $150 per passenger.