that this machine will have a limited upgrade potential and that it's unbranded, it looks fine.
You may be able to add more RAM, you may not - there's no way of telling - but a year down the line you'll probably want to do that. I would want to do it straight away, particularly if I took the Vista upgrade route.
I would also be looking for a larger hard drive on what is essentially a multi-media computer.
I have no personal knowledge of the supplier, so I can't comment on the customer service aspect of things, but that's something else you should investigate.