On a fairly regular basis, I travel to speak at specialty retail related conferences and expos. One thing I like to do is compare notes with other point of sale vendors and suppliers who are also at the conference or expo. Usually, I find out that the other companies have very qualified technicians and skilled salespeople but they don't have staff that has actual retail, restaurant or bar experience.
I feel strongly that anyone who provides cash registers or computer-based point of sale systems needs to have 'real world' experience. If they have never "walked in your shoes', how can they understand what you solution you need. It also shows when working with support/technical staff - they have a vested interest in helping make your business more successful.
End point: When searching for a point of sale system for your business, ask the vendors how much experience their staff has working in actual retail and hospitality environments.