Thunderbolt pretty much gives you the best possible compromise these days. Granted, no laptop will give you the power of a desktop, but if you can get by with less power, Thunderbolt lets turn your MBP or Air into a high screen real-estate workstation with mouse/keyboard/speakers/fast storage by plugging a single cable.
To me the ability to pull up my laptop and go work somewhere else for a few hours, or have my main workstation with me at conferences, etc is well worth sacrificing some power. Sure I can make use of multiple large displays, but I can do a lot of work without them without losing much efficiency. For stuff like design where I really need it, I can wait til I get home.
Sounds too good to be true, and it is. I tried this exact same setup and the noise the new MBP (was a 15" model) make when not even under full load is nothing i wanted to experience all day. It also got really hot in the upper keyboard area.. I those issues werent there, it would indeed be perfect.
To me the ability to pull up my laptop and go work somewhere else for a few hours, or have my main workstation with me at conferences, etc is well worth sacrificing some power. Sure I can make use of multiple large displays, but I can do a lot of work without them without losing much efficiency. For stuff like design where I really need it, I can wait til I get home.