There are ups and downs with this case, as there are with most products.  Unfortunately, there isn't a huge market for an after-market transmission housing for the E-Maxx so there's little competition out there.  Multiple companies have tried their hand at marketing this product with little success.

rc4wd.com has one of the only aluminum transmission cases out there for the E-Maxx.  They don't manufacture the product, and judging from my communications with them, know very little about it.  The case does not arrive with a set of assembly instructions.  It's fairly self-explanatory, but the few differences to stock that do exist make assembly a bit of a trick.  Even when the whole thing is together, it still doesn't seem right.  I had a handful of straggling parts left over, which I know were meant for something, but I couldn't get some of them to fit in any logical way, so they entered the realm where some socks go when you run them in the dryer.

Nevertheless, the transmission looks very good and being metal, resists harmful (to the gears) flexing.  It could be considered a must-have for extreme-power machines, and it sure looks good for those showy types.  If the added weight doesn't scare you, perhaps some other factors may.

The packaging is some of the worst I've seen.  The manufacturer actually tapes the baggie of screws to the case so every hit nicks and scuffs very visible marks into the side.  No attention is given to making sure these parts are separated for shipping rigors.

After assembly, there is some rubbing (resistance) in the motion, but only at full gear-change extension.  The bad part is, there's no middle-ground, as far as your shift servo knows.  This seems to be unlike the stock transmission's smooth function.

If you try to contact rc4wd.com about the problems you experience, you'll probably get a reply, but it's short, cold, and useless.  They just don't seem to care.

All in all, if you have to do it, and you're pretty handy, go for it, but know what you're in for first.