I picked up the new Rubicon M4A3E8 kit yesterday, and have been playing around with it since then.
The first point is that this kit marks another milestone for Rubicon. It's pretty much an entirely new kit - not much remains of their original (discontinued) M4A3 kit. There are 4 sprues packed with bits, including optional parts, accessories and crew figures (well, half figures). The precision and accuracy of the detail is up there with their best kits, but you can also have a lot of fun personalising the model. It's also going to be easy to build several 76mm-armed Shermans and have them all looking different. So I think this is their best kit yet in terms of just being enjoyable to build.
The most important options are the tracks and suspension - there are 3 versions, and they take up a lot of the space on the sprues. The basic version is virtually identical to the original, except that the chevron detail on the treads has been mounded onto the front section (but not the back - the only real flaw in this kit). The extended end connector version is very nicely cast, and a good example of how Rubicon are prepared to push the envelope with one-piece castings. They will fit on the original M4A3 kit, so I may replace mine. They don't fit on the M10/M36 hull. As an aside, the extended end connectors often broke off, so you can remove a few for added realism. You only get enough pieces for either the basic tracks or the version with extended end connectors.
The HVSS suspension is one of the big attractions of this kit, and it's very nicely done. All the details are there, and once again most of it is a one piece casting (although the tread detail is still only on the front section of the tracks). The tracks are the later T80 type (distinguished by the chevron tread pattern), which were less common in WW2 than the T66 single pin type.
There is one basic hull, with optional parts for the VVSS and HVSS suspension. The HVSS suspension involved narrow mudguards down the side which (along with the wider 23 inch track) altered the Sherman's appearance significantly, and these are separate parts which slot on very neatly. The hull hatches are separate, and other details like the rear plate and exhaust deflector have been greatly improved. Even the spare tracks brackets have been improved (remember not to mount these on the HVSS version).
The turrets have been totally redesigned, and look very accurate. As the instructions point out, you should only use the later version for the M4A3E8 (only very early M4A3E8s had the circular loader's hatch). The machine-gun storage brackets are included (they are a bit fiddly). You can't build 2 complete T-23 turrets - you have to choose. I don't think that's an issue. There are two .50 cals, one with a slightly thicker barrel for wargaming (a nice touch - I hope this becomes a standard feature in Rubicon kits). The M36 turret fits the new hull easily - as the M36B1 was often fitted with extended end connectors, you can now build a very accurate model of one.
There are 4 crew half-figures, all identical except 2 are modified to attach inside the hull hatches. No doubt most of us will replace them with figures from the forthcoming US tank crew set. The accessories include jerrycans and spare tracks and wheels (for the VVSS version) which are basically from the Allied stowage set. There are no spare HVSS wheels. There is an unusual version of the Cullin hedgerow device - these would be very rare on this Sherman, which entered service after the US Army left the Normandy bocage.
So, in summary a very good kit, and a very promising start to the Sherman range. Go out and buy some!