Ok, some more details on those M3's.
The models are Italeri Kit 7509, part of their Fast Assembly range.
I picked mine up for £6.50 for one of my 2 local model shops, you can probably get them cheaper off the internet but I like supporting my local shops and it avoids any postage charges. My Italeri M8 Greyhound was £7, so for 50p less you get 2 models instead of one.
Ok, it's not quite a direct comparison. The Halftracks don't come with a sheet of decals or a full set of instructions. Instead there is a single exploded diagram on the rear of the box. With only 14 parts for each halftrack the diagram gives a clear idea of where each piece goes, but does not give correct order to assemble the parts in, more on that later.
The box says that glue/poly cement is required to assemble the model, but in reality the various pegs and clips fit together tightly enough that gluing is not required. The headlights are the only item the needs a spot of glue to ensure they both stay at the same level.
This is perhaps where I made my first mistake, I decided to speed up painting by spraying the sprues with Chaos Black before removing the parts from the sprue. The parts fit so tightly that even a thin undercoat made the parts hard to slot together. I'd recommend not trying the same short cut I used
Problem number two was Part number 11, the windscreen. With only a single diagram to assemble by I'd assumed that the best way would be to put the parts together in number order. If you take this approach it's not possible to insert the windscreen/dashboard part into the chassis. I'd nearly finished the first model when I discovered this, then I found that the Fast Assembly system also made it very hard to take the model apart. It took me longer to pull the model apart than to assemble it in the first place.
Once together the models look right at home next to the M8. While there isn't the same level of detailing/stowage items etc. the models feel really sturdy and should hold up really well to wargame use.
As Iain said, the MG is post mounted in the rear of the truck, not cupola mounted over the drivers seat. This doesn't make too much difference to me, but might to some.
If you ignore my assembly mistakes the models are fantastic for the price
you pay. I'm planning to pickup a pair of the Fast Assembly Jeeps (Italeri 7506) for my Mortar and MG teams so I have a fully mechanised army. Without these Italeri modes I suspect the price would have put me off.