I have been running my MMM V2 through the paces... So far she just keeps on rippin'
I posted this in another forum, but I thought it may apply here as well...
For those that have been asking about the fan wire rubbing issue that the V1 had.... Castle has addressed this issue. For those unfamiliar with this, look at the following pic of a mmm v1;
The case was rubbing the wires bare and in some cases broke fan plugs off.
---Patrick said this would be addressed, and it was. Their solution was a foam pad that conforms to the electronics and prevents the wires and such from rubbing;
Also, people did not like the fan in the MMM V1. They have had a very high failure rate.
In V2, the fan only comes on when the ESC is at 150F or higher;(patrick mentions this in another thread) Castle now includes an insert that addresses this.
On a side note, To prevent my E-revo from the possibility of looking like this;
I made a metal (Al) plate to cradle my MMM V2 in;
The plate is DS Taped and screwed into the chassis, the MMM is DS taped and Zip-Tied to the plate. If it burns up, at least the plastic wont melt too much.

(thanks for the idea, neil)
Anyway, Hope this helps others that are on the fence about the MMM V2. Its working great so far. Tho, with the support Castle has been giving, i'm not worried in any case. Even if it fails, they are on their game. They will take care of it.
Still my top pick for upgrading the e-revo
As for the abuse;
I have run my MMM on 4s and 6s.
I use a Tekno Neu 1515/1Y in my e-revo.
My gearing was 24/58.
I did full throttle into full braking.
High speed runs back to back.

Tall grass running (taller than the truck)
I was able to get my 6s batteries to 130F (2 3s zippy 4300's) oops
My motor to 203F (not good)
All the while my fan on my MMM turned on for about 2 minutes. The highest temp was 155F.
It was about 94F outside when I did most of my "testing".
When running my 4s set-up;
The motor hit 178F
The batteries hit 118F (2 2s true rc 8000mAh 15c)
The MMM fan turned on, but by the time I got the body off the truck to check the temps it had already shut off. so 148F when I checked it.
I have since, changed my gearing to 24/62.
My highest motor temp now has been 174F.
will probably move to 24/65 gearing.
the power of this set-up is incredible.
great job castle!