Pros: Lightweight, portable, easy to use, great build quality
There are 100's of reviews for this product, all covering differing subjects. Nearly all of them rate the product very highly.
This is not a comprehensive review. If you want a more comprehensive review, you can probably find it on the net.
I only want to cover one topic:
iPhone/iPad connectivity (Lightening Connector)
Yes, this DAC can be used with iPhone/iPad via Lightening connector!
1. You will need an extra cable (Lightning to USB Camera Adapter), it can be purchased from the Apple store here (I've tried a third party connector, and it doesn't work - so I suggest you stick with the Apple branded one.)
2. You will also need a male-male USB to USB Mini cable (I think one of these came with the E07K). I ended up getting a really short one online, making the whole connection less bulky.
3. Make sure that the E07K is charged, and then disable USB charging (Menu > USB Charge > Off). **This will always need to be disabled while connecting to iPhone/iPad - as it draws too much power from the device**
4. Plug the cables in, and presto! You should be able to hear audio via the External DAC.
5. If you want losless audio on iOS, I recommend VLC. It's easy to use and has a cool interface for transferring files to device over network :)