As an update, I've now got as far as entering my registration code, creating a company, and some invoices and purchase orders into the win2000 bottle installation.
Only issues that I've found so far are that sometimes the interface appears to have frozen, and you can't select anything. This is because you've managed to get an 'Alert', or 'Dialog', underneath it (and no - I have selected the always on top!). Solution is to drag the top window out of the way.
Printing is a little odd, but I use the Wine PS printer, and then ps2pdf my invoices. (I have a script that checks a special folder every 5 minutes, and anything older than a few minutes is automatically converted, and placed in my actions folder. I don't print to printers as paper costs!
It is possible to get this working multi-user - only requirement is that the database is shared. The locking works fine as well. Overall, this works very well. Definitely silver standard, apart from the fact that it is not officially supported!
Information courtesy of http://www.anothermouse.com