I would never have thought Marty knew stuff like myob but he's spot on. You need to decide what you want to control/untilize. Whether you want to track debtors, creditors, keep inventory, payroll, etc etc. Premier is the multiuser networking package and I think its not much chop. It can be quite unstable and if one person crashes its all off the system for that user to get on again via deleting a .lok file.
Its a good package though for the Low end market of which you are in. I don't think you're planning on being a multi national any time soon.
Yearly service agreements are a must if you plan to run payroll otherwise being out of date shouldn't be a drama unless your version is bug ridden and causes you grief.
Btw I'd buy it if I needed it even though I think its not great but it does the job it was intended for. Holdens aren't Ferraris but they get me to work if you get my drift