I have used a BA for a property purchase. The reasons were varied, but ultimately it was a time resource. I don't have the time to spend searching. The property in question required quite specific crieria(set by me) it took 7 months before signing. The BA showed me maybe 100 properties over this time. Offers were placed on about 12. One accepted. How many were discarded prior to being shown to me... No idea.
The end value was below the asking price, could I have negotiated a similar deal? Maybe... But I simply would not have found the property in the first place. Has it achieved better than market performance? Don't know, don't care.
I was happy with the service I got, and hear from her regularly.
I think BAs have a place. If you are ' Proffesional' investor, and have the time, resources, regular contact with industry pro's, market knowledge etc etc etc I can understand why you wouldn't need to use one.
For me, I don't have these assets, so need to pay for them.
Blacky