I have the Acadamy Achilles, Warrior MCV and Stuart 'Honey'. The Achilles is building up nice, but has a few problems:
1) One interior fits all! The Achilles is based on their M10 kit and has incorrect internal ammunition stowage - ie the M10's tubes not the exposed 17 pdr shells (I'm procrastinating with casting from the 5 shells you get with the kit), lacks some of the sten gun racks, etc
2) Nasty ejection pin holes on the interior of the turret components and some of the other parts
3) Hull top is slightly warped but I expect it will glue down okay.
4) Rear hull tool stowage is for M10, not the British Achilles, and the outline guide for placement of tools needed to be sanded off. Fire extinguishers need to be sourced elsewhere too.
5) Muzzle brake is too small in shape and needs to be replaced.
That said, you get some really nice extras with the kit:
1) Two full sets of roadwheels (spoked or solid) as well as a couple of late war pattern 'flat' type for spares, two different idler and drive sprockets and two different track guides. (Spoked road wheels are great to replace the old Tamiya M3, etc)
2) Choice of 2 transmission housings (although one looks to be shaped a little incorrect)
3) A series of numbers, letters, buckles, wing nuts that can be shaved off 'sprue' extensions. These are for casting numbers, etc.
4) Track blocks, spare links, radio, etc meant for American vehicles ie M10
5) And given the above, a whole set of M10 round containers
The Warrior comes with a choice of building with or without add on armour. If you do fit it, it needs some work to improve (drill out access hole for external fire extinquisher, etc. The layout of the rear hull tools also needs to be corrected when checked with references.
The Honey has the same 'one interior fits all' problems and needs a fair bit of work to correct to the British version. If you are going to put a figure in it, or leave the hatch closed, this kit is (apparently) quite good externally.
Also be warned, some of Acadamy's kits are old Tamiya mouldings and not new kits at all. Despite all this, I feel the kits are superior to Italeri and roghly comparable to Dragon (DML), but not as good as the more recent Tamiya offerings.
Zvezda is hit and miss in quality, usually simplistic and a little unrefined. Think early 70's standard of kits and you will know what I mean - thick plastic, sometimes a bit 'greasy' or brittle, heavy detail, flash. Just remember, you get what you pay for.
I haven't built any trumpeter kits myself, but a few guys in my club have -(Swedish S-tank, Challenger, Sam 2). They all say that the quality is good for the price, but be prepared to do extra work if you want an accurate and detailed result. They too, as WIPW (Bill) has stated, recommend care in cutting the brittle plastic.