I don't agree with Udo about the rating, but honestly, this is the kind of review I like to read here: a different opinion.
At this point I'm kinda bored to hear again and again, how much this mission is a masterpiece. Giving a rating of 1 is a bit cruel (I think it's a relatively decent mission with lots of interesting aspects), but yeah, definitely not the masterpiece most say. Has some serious pacing and game design problems.
While the mission's size can be explained by the fact that it was built for the Summer Speedbuild Competition, I think it's completely fine as it is (perhaps the outside area could be more detailed, but that's all). I wish more fm authors would consider building small sized missions (which you can finish under 1 hour), not everything has to be an epic 2-3 hours intensive thievery. I sometimes mind a bit that the more experienced and talented creators avoid thinking in smaller scale, but cons...
Hmmm, I'm not 100% sure about the "beginner's effort" part, but I can definitely see what you mean by that. In terms of quality the mission isn't too consistent (also there are a few parts which kinda have an unfinished/abandoned vibe), but I think some areas were really well built in terms of annention on details, asset placement, usage of textures, etc. (not to mention the wild ideas of the second part)