Like you, I've had reasonable performance from Clevo/Sager for software development. One thing I would possibly look for: Get the _heaviest_ laptop you can find with them. Those typically have much more aggressive cooling systems than the lighter models. Case in point: Sager 9377s at XoticPC. If you go to the gallery and locate the view of the bottom of the laptop, you'll notice multiple intakes with extensive venting out the back. XoticPC in particular can do a copper cooling upgrade which might be worthwhile to evaluate. (Haven't tried it personally)
I'm mentioning XoticPC in particular because I've gotten 3 or 4 laptops through them and have been happy. They're pretty slow to ship for custom options (they don't keep a ton of custom parts in inventory), but I've been happy with the customized product.
Laptops will always be a bit of a problem due to small packaging/weight requirements, but perhaps these tweaks can help get you there.
Just about every computer on the market today runs Unix, except the Mac (and nobody cares about it). -- Bill Joy 6/21/85