I'm probably going to get panned here but for a truly portable computer a netbook beats an ultrabook every day of the week for me. Ok so not those early netbooks with only 2hr battery, big black bars around the screen, a poor excuse for an SSD and a cut-down OS.
For example, my Asus 1005HA-P netbook... 2GB RAM, 1Kg, under A4 in size (slightly thicker than an ipad), VGA, ethernet, 4 USBs, webcam, SD card reader, WiFi, Bluetooth, 9hr battery life so enough for a day of airports and flights (even after 3 years I'm still getting 9hrs). So it's not got the most grunt in the world, but with Win XP it's decent enough for everything I need to do when travelling... Office XP goes like stink, VLC and MPHC play HD video, Firefox goes on the internet, Pidgin sends instant messages, Skype works, GIMP opens to resize/crop images etc.
In addition to that I have an Acer Core i5 laptop, which could be the same spec as an ultrabook, about 1cm thicker, same width/length, has better connectivity*... all for 1/3rd of the price. The higher price and thinness of an ultrabook doesn't justify the 200%+ price differential over a normal laptop.
* Needing stupid adaptors for ethernet and VGA/DVI connections is a complete joke. The last thing I want to be worrying about when travelling with, you know, a lightweight portable computer, is having to pack adaptors for essential connections like that. Fail.