The Innokin intergrated batteries are a great step up from Egos - the only disadvantage to them is the integrated nature of the battery, so that when you've exhausted it, you have to replace the entire unit, though I believe the high capacity of the MVP means that they need charging so infrequently, they have an excellent lifespan.
I have an Innokin VV v3.0, which is similar in principle, but is more of the Ego proportions and I love it, but I am now upgrading to the SVD, which has separate batteries, so it'll last until I break it (or the next bout of shinyitis attacks - which will probably happen first).
To be honest, I think if were looking for a box mod, I might also consider the Innokin VTR, which has replaceable batteries (and it is quite handsome, as box mods go), though they are more expensive (myepack £60 vs £36 for the MVP)