It is certainly a Mahonia. I didn't know that the berries are fit for human consumption, but I do know that the birds love them.
It is not a plant that I find 'attractive' and can see why it is 'out of favour' but it does have extraordinary plantability in a hedgerow or a boundary. It becomes a useful backdrop plant for a border if kept in check as its flower spikes are a perfect spring yellow blooming higher against an otherwise dull fence or boring green hedge.
Keep it but don't let it grow rampant if you don't have the space.