I have had a Total Bithead Clear for about a year now - my first headphone amp - and for the money, it was a great bit of kit.
I used it occasionally as a DAC via USB from my laptop, but mostly as a straight headphone amp from my iPod, connected via the iPod headphone jack and running Shure E3c's.
I am upgrading now to a Predator as I finally have my Shure SE530s and a decent LOD cable on it's way, but the Bithead served me well as my introduction to the world of headphone amps and was definitely a clear cut above using the headphone jack from both the iPod and my Macbook Pro.
I liked the sound on the whole and I did like the cross channel mixing function/effect, especially with IEMs.
I found having to use the disposable batteries a bit annoying and it can't charge rechargeable batteries either, so you will need to stock up on AAAs if you are using it away from a powered USB source.
Seemed robust enough - certainly I have dropped it a few times with no ill effect, though I am not that keen on the rubberised battery bay cover....
Um - so yeah, on the whole I like it!