I've been playing acoustic bass guitars for 10 years - well not strictly speaking 10 years, I have slept as well.

My current bass is an Ashbury 5 string in walnut and spruce. It has a bridge pickup and graphic EQ and cost about £300 a few years back. In the context of a ceilidh band, it gets put through a PA and I have no problems with feedback, but then we don't play at ear-splitting levels, but in any case, a decent notch filter should sort out any problems. My perception is that it sounds different to a solid electric bass and one big advantage is that it is much lighter than my electric bass so is not so tiring to play. It is not loud enough to play in sessions or clubs without an amp. There are some luthiers who make large bodied acosutic bass guitars which apparently can be heard in the context of a session without an amp.