The M1330 is the one I'm leaning towards. You can get them with Ubuntu installed direct from Dell (http://www.dell.com/ubuntu or http://www.dell.ca/open in Canada).
If the machine is important for work then don't get a consumer model.
The XPS and Inspirons are consumer models. If something needs to be replaced the tech support people (soon Philippines based, if you haven't read the news) will tell you that they'll send a tech in 3 to 5 business days. There's no international service and depot service takes longer still. Before you buy an XPS or Inspiron ask yourself if you can live without it for a week.