I love the ultra portable Thinkpad X220 and was looking at building a desktop PC for gaming but that involves having a dedicated machine, monitor, build cost, two OS to look after, etc. The idea will be to build a custom box for the graphics card and power supply and have it like a dock at home for when I feel like gaming I can just plug the laptop in. I looked into gaming laptops but again the cost and size put me off as I use my laptop for work a lot.
If you use an Nvida card it uses Optimus drivers and can display the image on the laptop screen so no need for an external monitor! I'm heading round a mates tomorrow to test out the adapter with his GTX560 and power supply before buying anything just in case it's rubbish. People say it can give 15,000 3DMark06 points so more than enough for gaming considering the built in card is about 3000 points!