Ubuntu has years worth of work before it will be ready to use, and I expect that it will never reach the level of stability of iOS, or even android. The Ubuntu team always has great ideas, botch the execution of them, are really slow (fast in Linux time) to fix the bugs, and usually introduce more bugs with each release. Money drives this industry, and Linux is really bad at making money. That is also a big part of google's problem with the fragmentation of android.