Picked up a 4.1 kit yesterday. all these yrs of used b4s just wanted to sit down and build 1 new outta the box.
Well a few things i find less than 'associated'.
1st. The known quantity of the weak chassis issue up at the 'chin'. AEs remedy for this problem (til the present stock of chassis run out i guess) is to use a carbon bulkhead to strengthen it. i did, we'll see how it goes.
Where do you get a carbon bulkhead from? Also, they slightly reinforced this area compared to the B4.. look and compare
2nd. Battery posts alignment where the all thread goes thru for the nuts to spin on. i had to run them in point just slightly outward and massage the holes in the strap, ovalizing them just a bit for the spin nuts to seat correctly.
3rd. NO Rear Wheelnuts? You serious!
I believe it... my T4.1 only came with 11 diff ball... called AE and the guy told me "it should be fine." 
4th. The new ball cups, well i'm not goin to use them as i've seen how rubbish they truely are since most every1 got a 4.1 before i did. older or RPM units for me.
Losi whites for me... they look so nice and strong as hell!
5th. Rear T-Plate angle in back leaves huge gap in between itself and tranny such that when u place tranny in the rear u think u've done somethin wrong. relying on those 2 rear screws for the motor guard to pull everything flush is not right at all.
6th. Clunky CVAs. 1 unit was fine, however the 2nd was horrid after i tightened the setscrew. loosen it and it was fine. tried other side of barrel in the cva. same result. had to use some cutting oil and fine abrasive to slightly work in the unit, then it was gravy. perhaps something that works itself right in 1st run or 2, still off putting.
Don't need the set screws thats what the retainer clips are for.. less binding
7th. You give me stealth lube and black grease, but no green slime or loctite blister pack?
+1
8th. New tranny case and thicker motor plate, but same size tranny screws. cant use washers unless u want ur motor plate come loose. New tranny case also has interference w/AE Zinc block weight made for the car.
I still run the old motor plates to assist with motor offset.. FT Lipo ballast fits fine in my B4.1...
9th. other kits have their bellcrank spring already preset/prethreaded. very easy task to kill the threads in the 1st step of the kit. i didnt due to experience, but others might might cry in their beer or their milk at step 1.
10th. Oh yeah, the thicker motor plate makes standard 3x2.5mm motor screws not work or on ragged edge of grasping the motor. i'm sure some folks are stripping threads innocently gettin those nice new 85$ motors in and the screws can hold it or tear 1st thread out b/c thats all they are holding.
Again, just use an old motor plate if its a problem... shouldn't be though.
Fix these issues on 2nd run.....or just put the b5 out already and end the speculation and endless banter on the internet.
YES! +1,000,000
R