Transparent, at all frequencies.
Respect of the soundstage (from a small jazz club to a stadium in a click).
Full of possibilities (a lot of inputs and outputs including XLR).
Rock solid.

Not that cheap, but sort of a bargain for this level of perfection.

After some years with a fantastic Krell 300il, I upgraded to a MBL5011 and 2 MBL9006 pre/mono amps setup.
The change is huge and concerning the pre MBL 5011, it certainly is the most transparent pre I have ever heard (far from the 300il pre section of course, but also better than an old Golmund Mimesis I owned a couple of months).
Everything seems to flow through it, whatever you give it. I used a 3dLab DAC2000 first and upgraded recently for a MBL 1511F.
It is also quite easy to use and full of possibilities (but I mainly use one of the tons of inputs and one of the 5 outputs).
As my setup is symetric from source to amps, I use XLR in and out (with MBL cable) and I can only recommend using it as a default (a bit deeper on complex and big soundstages, performers even more stable).
It can be seen on http://mbl-hifi.fr/catalogue_mbl_5011.html

Customer Service

Extraordinary packaging, very Apple like.
Perfect. I had a problem with the remote, it was changed immediately.

Similar Products Used:

different integrated amps owned or borrowed used as pre (Krell 300il, MBL 7008),
Goldmund Mimesis (21?) borrowed