I run a 5 yr old L300 Toshiba which has performed faultlessly since new. It has a 15.6" screen, 250Gb HDD, runs a Pentium Dual Core T4200, 2.00Ghz CPU and 4Mb of RAM (I doubled the RAM from the original 2Mb, a 2 minute task and not expensive). The CPU was mid-range at the time or purchase. I've never had a problem with any task processing.
I chose a 15" screen because it's an ideal size for a laptop. Then, there's the weight problem as well.
The L300 weighs 2.7kg, it's as heavy as I want to lug around airports and public places.
I know the latest models are getting lighter, but there's also a good balance between weight and strength as well.
I've accidentally dropped the L300 off a bench at the airport security counter, and it bounced and was completely unaffected by the drop.
However, it was also inside its padded Caselogic carry bag, which is also a vital accessory.
I'd buy another Toshiba tomorrow, and I've been checking out the latest offerings from them, as I'm looking to upgrade soon - and they look pretty good to me.