margetti:
I went from the CX-300's to the 110's and have found them to be an excellent upgrade, although I got them from Play for £19 during their December Monday madness offers - which tends to make one less critical than when spending £80-odd.
I too found them a bit dull the very first time I tried them, but when I went back to the CX's for a further comparison, the CX's sounded horribly harsh!
One thing though - they have very much exposed the limitations of 128 kbps AAC, to the point that I will, over time, be re-ripping my CD collection at maximum bit-rate (still procrastinating over whether to go AAC or MP3).
I would not call the CX300s harsh, I would say they're revealing and honest. Which format are you listening to? From my experience AAC has always sounded smoother on iPods, and MP3s are a bit harsh - but I don't even find this a problem with my 3g Nano and the CX300s.
But as you say, maybe I need to give my SE110s another chance, I'll come back after two weeks of listening.