The novel's ending is a debate unto itself, with critics and readers alike split in their opinions. This is the very last line of the book*, and it represents an anti-climax to some, but a symbol of greater meaning to others.
Michiko Kakutani's mixed review of the book posits that Wallace's writing style is something akin to a 'word-machine' which is suddenly turned off, "leaving the reader – at least the old-fashioned reader who harbors the vaguest expectations of narrative connections and beginnings, middles and ends – suspended in midair and reeling from the random muchness of detail and incident that is Infinite Jest."
Daley Haggar's review for the Harvard Advocate invokes Umberto Eco's idea that a text is "a machine for producing possible worlds." He advances the idea by suggesting that "the world itself seems to have become a machine, generating multiple competing realities (the reality of drugs, of the media, of entertainment as opposed to life) [...] For the characters in Infinite Jest, this phenomenon makes life as it is being lived (after all, we can only really live one life) both true and untrue."
This blog entry takes an interesting look at the ending, tying together various strands of the novel in order to conclude what else may have happened beyond the pages as we see them.
All well and good, but what can literary criticism do that a sharp needle and some ink can't? This guy loved the ending so much, he had the final sentence permanently appended to his body:
* Or at least the main body of the text, as it's followed by 97 pages of footnotes. Which would've made for a more cumbersome tattoo.