I'm thinking of buying either a macbook or a laptop soon, are there any compatibility issues with a Mac and your software?
Is it just a USB port that is required to interface with your ECU?
The software wont work with a Mac, unless you dual boot it with a Windows partition - even then you're in a potentially bad place as USB to serial devices are not all the same, I always recommend the ones from www.easysync.co.uk
I'm pretty sure that one of these ASUS mini laptops would be perfect.
As for tuning tool, I haven't used any better than my trusted old ThinkPad X23. And I've used a lot of different ones. It has low weight (1.5kg's), VERY rigid and sturdy case (Magnesium alloy frame together with plastic that consists of carbon-fiber), normal 12,1" XGA screen and I bought new 4400mAh battery which makes it hold charge for more than 4 hours. Plus it's cheap!
Only drawback is a lack of COM port but I bought an adapter locally that has worked absolutely flawlessly for two years.