105 is a great group and is more than adequate for a beginner. from what I have heard the ultegra and dura ace will give you slightly smoother shifts but mostly you are paying the extra money for lighter components
+1
I've used 105 for several years, and have never had trouble with it.
Unless you count in the occasional snob looking down his nose at someone not using Dura Ace, SRAM Red or Campy Record, that is. But I do not care, though

I'm happy with 105 no matter what others think about it.
Maybe the 105 require a more frequent service interval than Ultegra or DA to remain precise, but you can tell when it's time for service by how the components feel and sound. And most good bike shops can do this on short notice without charging a lot for the job. So, not at problem IMO.
If I were to upgrade anyhow, I'd consider SRAM Force rather than Ultegra. The Force group is deemed a small notch better than Ultegra, is lighter and less expensive. And, many Shimano and SRAM parts are compatible, so I could re-use a lot of my current 105 components.
But I can't see any
really good reasons for me to upgrade from 105