Pros: quality, price, design, controls, durability
Main feature of Fiio E7 - it's multi-purpose usage possibilities. USB DAC and portable headphone amp in one compact and small body.
Specially I'd like to mention following:
- Design. It's really nice and stylish
- Long operation on one charge
- Perfect sound (really like it)
- Good control
I'm actually using E7 in two ways. First, like a portable amp for my iPod Nano, together with Mee A151 and Grado SR125i. But I think I'll use Fiio E6 now for that, it's much more portable, but sound really good (little worth then E7).
Second usage - I'm using it together with my MacBook Pro with perfect player Decibel. When used in hog mode - E7 sounds much better then built-in audio-card, especially with Grados.
Also E7 gives nice bass boost with EQ. It doesn't trash sound like all software EQ does, but gives very nice and soft impact for bass and lower mids. It's especially noticeable on brass.
So cost-wise, this DAC/amp is outstanding.
Few photos (cant's embed them, so just links):