Pros: Clean, Lean and Multiple Settings (Extra Battery & Charger Included)
Cons: None really, but opening/closing the case is funky.
I purchased my E11 bundled with an extra, larger capacity battery and a charger off of Amazon. The additional items added a miniscule amount to the total, but greatly increased the overall value for me. It also negates the biggest gripe that folks have about the E11, which is not being able to use it while charging. Opening the slim cover without fingernails or a guitar pick (or the like) isn't all that easy and closing it makes the cover flex a little, which is a little scary. Nothing has happened with it... yet.
If you are using the headphone jack on your portable audio source, this amp may transform your mobile audio experience greatly. I use it with my 1st Gen Zune 30 and a host of IEMs and 3 full-size cans (JVC HARX900, Shure 440 and Superlux HD681). I only use an LOD for the cans, but both outputs are viable for IEMs. It has three bass boost settings (0,1,2) two power settings and two gain settings to adapt to your phones' impedences. It pays to experiment with the settings if you aren't impressed with your initial sound. Fits in a pocket, even strapped to the old Zune... Very clean, very powerful and very adaptable. I like it a lot.