The most commonly seen criticism of the Wheel of Time is that it is verbose. This criticism is manifested in several ways.
Verbosity of Detail
Many readers complain that Robert Jordan spends unnecessary words on minutiae, insignificant events (such as characters' clothing or personal habits) that do not affect the plot. There are three typical responses to this criticism. The first is that Jordan's high level of detail makes the setting and characters far more "real" than those of less verbose authors. In The Lord of the Rings, minor details are glossed over, but whether this is to the benefit or the detriment of the story is a matter of personal taste. The second is that even minor details often become important, and to mention only details that would become important at a later date works against suspension of disbelief – how do the characters know in advance what details will become significant?. The third is that this is simply Jordan's writing style and, as has been noted, a matter of preference. Jordan's tone has not changed significantly since the first book, so those who disliked the first book for verbosity of detail would probably feel similarly about the rest.
Verbosity of Plot
Another complaint is that as the series has progressed, the books have "bogged down". In the early books, the characters wander about seemingly at will, unfettered by (or flouting) other responsibilities. While the results are "exciting", they are unsustainable for obvious reasons. As the plot and characters develop, less time is spent on explosions and more on the real consequences of the characters' actions.
Much of this is attributable to the scope of the setting. Tolkien's world consists of few divisions. In the South, where most of the action takes place, there are basically two "good" nations (Rohan and Gondor) and one "evil" nation (Mordor), all of them essentially stagnant but for the events directly related to the story. The world of The Wheel of Time is far more complex, with over a dozen important nations and more minor players, each with its own culture, traditions, history, and politics, none of them "good" or "evil", and all tossed in disarray by the Seanchan Return. This makes their interaction significantly more complex than 'good nations unite to fight empire of darkness'.
Verbosity of Story
Many people complain that the story is simply too long. This is basically the effect of a long, complex plot compounded by the two previous points. Different people have different tolerances for long stories, and many people's max out at well under ten thousand pages. These critics often point out characters, events, or plot threads that they believe could be dropped. The claim that Robert Jordan intends to keep the series going forever is, in addition to being unfounded and rather insulting, disproved in light of the imminent end of the series. Robert Jordan has sworn that the twelfth book will be the last, although some suspect that a thirteenth will be necessary.
Critics comparing The Wheel of Time to shorter works like The Lord of the Rings might compare them both to Mozart's and Wagner's operas. Both are highly regarded, but their forms are much different. Mozart's La nozze di Figaro is, like all of Mozart's work, marked by his trademark economy. It is not excessively short, but nor is it particularly long. One gets a clear sense that not a single note is wasted. Wagner's Der Ring des Nibelungen, on the other hand, is so long that it cannot be played in a single sitting but is subdivided into four sections. The orchestration is dense, the motifs frequently repeating. Unlike the small orchestras of the early classical, Wagner calls for a huge orchestra containing both common and obscure instruments, including one he invented himself. One can be certain that if a few notes were omitted, few in the audience would be any the wiser. An attendee not a fan of Wagner would almost certainly be clawing at his seat in boredom within a few hours. Given this, is Wagner's work somehow inferior? Certainly not.