The problem we've had with Intel's Ultrabook initiative is one of consistency. We've seen Ultrabooks we'd be happy to carry around, and others that bore more bulk than we expected. Because those more rotund models employed larger displays, though, they were still able to skate by with Ultrabook branding. That's watering down the concept, we think.
I've heard this being said countlessly, not to mention things that are outright wrong(where Verge claims Intel is diluting Ultrabooks because the Zenbook U500 is one. It actually isn't, because it uses QUAD CORE CPU when Ultrabooks require a ULV platform).
It's about being better in average. You can find a phone that's near 7-inch Tablet in weight and size. You don't hear as many complaints do you? But you know in general a "Phone-class" hardware is smaller than "Tablet-class" hardware.
It's likely that lot of people who will buy even "heavy/big" Ultrabooks come from even bigger 5, 6 or even 7, 8 pound systems. Those that bought relatively thin and light systems will see even thinner and lighter systems like the Aspire S7 with 12mm thickness or Lavie Z with 875g weight.
In conclusion: Unnecessary complaint