Buggy text and inappropriate art have been hallmarks of many, if not most, versions of Traveller. Personally, MGT seems to be the least buggy version since original Traveller. MGT, unlike some version of Traveller, including T4, is playable the moment you crack the book. MegaTrav, T4 and TNE had books of errata. MGT, not so much.
As for the quality of art, yeah, much of the line art in MGT doesn't make the cut for me. Some of it does, though, and the shaded/painted art, for the most part, is very good.
Classic Traveller had the advantage of not actually having much in the way of art, so what they had was good. MGT actually has a great deal of artwork in it. TNE featured quite a bit of dodgy art, MT got around that by recylcing the best art work created for OT, and Treveller:2300 was all over the place as well. 2300AD cleaned that up nicely, though.
I've been hearing bad things about Mercenary, to be sure, but I haven't seen it myself, so I'll reserve judgement.
Otherwise, I like MGT. I like the mechanics. The books feels fine. Not exceptional, but fine. With two exceptions, the illustrations don't offend me. Could it be improved? Sure. So could 2320AD...
As to the charge that Mongoose doesn't seem to
get Traveller, well, I don't think they are trying to. That is, they are not setting out to cater to long-term Traveller fans. They are trying to bring in new blood. Judging by their sales figures, they have been successful in doing so.