Not as bad as you've heard. There are actually some funny parts and Affleck and Applegate have fairly good chemistry. Applegate, in particular, is appealing and likable as Affleck's love interest. James Gandolfini and Catherine O'Hara are consummate professionals. They're pretty good in just about everything. In the end, "Surviving" is not the worst holiday movie you'll ever see.
Unfortunately, it is unfocused and much of the comedy is forced. The attempts at dark humor come off as dour. Affleck tries hard to be endearingly spastic and overenthusiastic but comes across as disturbed. His character's cartoonish nature is brought into high relief when viewed next to Gandolfini and O'Hara's more muted, believable performances. Even by the relaxed standards of holiday movies, you never fully buy into the set-up of Affleck "renting" this family for X-mas.
There are also scenes that border on the surreal in their strangeness. The X-mas eve scene replete with incestuous humor (a son being discovered looking at naked, provocative pictures of his mother) that not only isn't funny or believable but disturbing.
To make matters worse, the colors in this film are muddy, almost noirish. The house set on which most of the movie takes place looks stagey and cheap.
"Surviving" is mostly of interest as the fourth in a string of box office duds (Paycheck, Gigli, Jersey Girl, and this) for Affleck. It remains to be seen how lasting the damage will be.