The Sony is old & under powered and the Gateway is a monster for the past and is more of a joke than anything else. But the Dell XPS M2010 is a more serious compititor for the new iMac in my opinion, although it is way overpriced. I don't understand why Dell markets it as a laptop.
http://www.dell.com/content/products/productdetails.aspx/xpsnb_m2010?c=us&cs=19&l=en&s=dhs&~section=specs#tabtop
In the immortal (and barely relate able) words of Zap Brannegan: "She's built like a steakhouse, but she handles like a bistro"
That's one huge laptop