Your point of reference may have changed now that you got used to it. It is like first jumping in a fast car coming from a slower car and being amazed but after a while you get used to the speed and maybe expect more?
Without quantitative speed benchmark stats, it is hard to say if you are right or not. Try running some sunspider or geekbench tests to see if you are valid.
From my experience, I do notice when the A6 processor throttles itself to lower speeds when battery is low to conserve energy. I can confirm this by opening Geekbench 2 and seeing the CPU reported to 600-800MHz vs the 1.3GHz when under load or charging when the CPU ramps up. That may be what you are experiencing?