I have a Viking/Husqvarna Diamond. LOVE it. I upgraded from the smaller Ruby. This one I purchased on Ebay if you can believe it. I would not hesitate to buy a used one providing the seller is open to you playing with it before purchase. I got mine from across the country, saved a TON, but did end up spending another $200 for a tuneup. Was well worth it in my book. I now have a top of the line machine and paid well under half of what they were asking for a new one. Craigslist sometimes can be a boon to find one, too. You'd be able to play with it then.
Just a thought: if you DO end up buying one from a seller online....ask them to embroider your name and address on a piece of fabric and send it with the machine (without cutting the thread off the machine) so you can see it was working properly when they shipped it to you.
Good luck!