First, let's look at the minimum specs for any handset to run Ubuntu:
- Processor: 1 GHz ARM Cortex A9
- RAM: 512 MB to 1 GB
- Storage 4-8GB eMMC + SD
- Processor: quad-core ARM Cortex A9 (such as the Tegra 3 or Exynos 4412; although the Snapdragon S4 Pro runs on the Krait architecture rather than ARM Cortex A9, it easily outperforms most other quad-core chipsets, so it should be capable of running Ubuntu)
- RAM: at least 1 GB
- Storage: 32GB eMMC + SD
Whereas Android runs on a combination of Java apps and the Dalvik Virtual Machine, Ubuntu runs mostly on C, which means that Ubuntu should have better performance than Android. Ubuntu runs either HTML5 apps or native apps built on Java, C or C++ with native OpenGL graphics support. Ubuntu also provides APIs to allow developers to build cloud services that "sync any kind of data to the cloud."
Other notes: don't expect much carrier support aside from (perhaps) T-Mobile, don't expect a native Ubuntu phone until 2014, but do expect a flashable image for the Galaxy Nexus in a few weeks. Also, popular apps like Spotify, Twitter, Facebook, Gmail and YouTube are already supported on Ubuntu for phones, and big-name developers such as Electronic Arts are currently developing apps for the new OS. Native lockscreen shortcuts to your favorite apps are also available, via the aforementioned partial swipe from the left edge.
Further information can be found on the Ubuntu microsite dedicated to phones, and I recommend viewing at least part of the video below before you make your decision. For my part, I basically scrubbed to the parts where the phone is being displayed, skipping most of the monologue
So do you think you'll be testing Ubuntu for phones on your Galaxy Nexus when it's (presumably) available later this month? Do you think you'll get a native Ubuntu device next year?