Regarding all the items you use, software and hardware make a list. Then goto the manufacturers website and see if its compatible with Vista. For example the Brother printer, goto the Brother website and see if theres a driver for it, same with the software.
If there is a Vista problem then see if the companies are creating updates which you can download.
If all of this seems to be too much bother then you still can get Windows XP. Dell still do it as an example and companies like Novatech will supply a blank PC and supply a OEM copy of XP Home, as an example, for about £60.
Without having a list of the software and hardware you use its impossible to say whether it would all work ok.
A friend of mine uses a program called Quickbooks for his business and he asked me about it, heres the website for it and what it says about Vista click here now I have to stress that this is just an example.
Whether you would have any bother or not really depends on whether the hardware and software manufacturers have bothered their backsides to make their stuff compatible with Vista, some have and some haven't.
I have to stress this is not really Microsofts fault, in my opinion at least, everyone has known that Vista was coming out and some didn't bother updating their programs and drivers. You would have thought that when Vista came out that it was a gigantic surprise to them.