I recently carried an older 13 inch MacBook Pro around to a bunch of meetings in the city. I could not believe how heavy it started to feel after about a mile of total walking.

I welcome powerful laptops that are as light as possible.

Where are people working that they need a full day of untethered charge? I've never been to a client that didn't provide me with a power outlet.

4 or 5 hours of real world use for a developer workstation is just fine train commuting or sitting in a coffee shop in the morning.