First, I do want to say that I;m much more of a Lankhmar fan than a Relams fan---prefer a low-magic setting & a bit more nitty-gritty than epic settings like the Realms or Krynn.
For the most part, I have to agree with Neowolf & Psion---it suffers from too many cooks (unavoidable with the sheer number of novels based in the Realms), & it is a bit too well defined.
It's this excess of detail which, IMHO, acts as a double-edged sword; it grants an immense amount of detail to work with, yet it's a mountain of reading in its own right. The works created for the setting can generate interest, but it can also bring about excessive attention to continuity & detail from the staunchest of fans.
I find the same problem to be true with other popular settings, such as Marvel, DC, Star Trek, Star Wars, Dragonlance, even Lord of the Rings, all of which have/had/will have RPGs based on them. I think that this problem is worse with ongoing sources such as comic books.
I don't like the high-powered epic feel of the setting; the gods are too involved in mortal affairs, & the Gandalf-like character of Elminster (even more so with his role as a sword-wielding Chosen of Mystra, much like the sword-wielding Maiar that is Gandalfl and, there is additional Chosen of Mystra as there are addtional Istari, such as Saruman and Radagast)---the personalities are different, but they are cast from similar molds.
And, as a final note, I dislike the use of an entire Egyptian pantheon in the Realms---it's been done before (Palladium Fantasy is a good example of this). I think I would accept it a bit more if it were more piecemeal, like a lot of the borrowed gods in FR---the Norse Tyr, Finnish Mielikki & Loviatar, Celtic Oghma, Roman Silvanus (listed as Celtic in the old 1st Ed. Deities & Demigods), etc. I don't mind this being done in homebrew campaigns, but it does bother me when it's done in published settings---if the deities are going to be invented, then go all the way instead of halfway.
I liked the Realms back in the old. 1st. Ed grey box days, when Drizzt only appeared in the Icewind Dale Trilogy, & I anticipated playing the original Pool of Radiance module. However, since the Time of Troubles, the Realms have lost its appeal for me.
Oh well, just MHO.