I have one of those replicas.
If you can get past the fact that it's not real (and that it's mostly plastic), it's actually a very good replica. You can disassemble it just like the "real steel," and it cocks/fires just like the real thing. The barrel is even removable. The mag that came with mine is, in fact, a real MP-40 mag, and there are other metal parts on the gun. For example, the entire folding stock is metal, the sling mount, the cocking handle (which also has a prototypical safety), the extractor (IIRC), the disassembly knob, the trigger, at least part of the lower frame (I think the frame around the grip is metal), etc. etc. It is so realistic that - if you put an appropriately sized wad of paper in the "breech" like I did - you can actually make it extract a real 9mm casing if you put the casing in there manually.
If you're in the same boat I was (a desperate fan of the MP40 who was dismayed at not owning something that at least looked and felt like the real thing), I would honestly say you should think about buying it if you have the money. If you can deal with the presence of plastic, it's a mighty good replica.
Hope this helps, feel free to ask me any specific questions (about this subject...) that you wish.