I have a launch day E7 and I abuse it almost daily. It works wonderfully to this day, with no build issues whatsoever.
Anyone expecting to hear BIG differences from anything that isn't a direct change of headphones, is a fool. There is sheer hyperbole here on Head-fi, but subtle differences and improvements can be expected. Subtle here tends to be misconstrued as MAJOR.
If you have a decent soundcard and headphone out that isn't causing major distortions, then yes, the changes won't be anything but slight and subtle going to the E7. The E7 is a decent DAc that gives you a clean signal to your headphones. What the hell else do you expect? Again, the most improvements you will ever get is going from one headphone to another. Everything else will change the sound in minor but good ways, especially if you've been in this game long enough to appreciate the slight percentages of improvements.