With mixed success, I'd say.
I've offered pre-gens for new games, & sometimes people went w/ it--mainly because the identity wasn't really established, but the stats were.
I've played in a game (actually, it was during the Night Below module) where players had severely limited character generation options, not to mention times when the players could only use characters whose players weren't present. The game was memorable not because it was so enjoyable, but because it was a bit of an arduous process (it had it's moments, but the non-moments far outweighed those IMHO). But, then again, I think that the game was doomed from the get-go, w/ real life issues & whatnot being a key issue.
However, I have run stuff where I hand a specific pre-gen to a specific player & have them play that. The character typically is designed for that player--I mix in aspects of that player's personality into the character, as well as that player's preferences as well (for example, the PC may be of a particular race of class the player often selects/plays/prefers). The PC names are a typical Gygaxian letter-jumble of the player's names. The PCs' ALs are ones that the players often play (not necessarily select, but play--there have been times when a player selects CG for their PC, but actually play the PC as CN).
The big catch is that
these PCs & their adventures are part of a side game that directly/indirectly affects the main campaign (and the PCs that the players have created). It's an effort to do a bit of "meanwhile" work, as well as a fun way to create interesting plot twists: the PCs get to town, looking for an ancient text, but another group of adventures beat them to the punch--the pre-gens, who just happened across the book while on a mission of their own. So, in essence, the players literally have themselves to blame for making their own lives harder.
For the most part, these pre-gens were a hit, because it had its own fun, weird dynamic: for example, 2 brothers who are members of our group were depicted as a half-orc rogue (the elder) & a halfling fighter (the younger). The half-orc was adopted by the halfling's family (which isn't far from the truth, since the elder brother is an adopted child), & it was a funny-to-watch dynamic to see played out. A husband & wife pair were a dwarf sorcerer (him) and an elf barbarian (her). One player wasn't as amused (didn't care much for pre-gens as it was), but all in all, it worked out better than I expected: the only reasons why is because I more or less tried to match the characters to each player's preferences & natures, & because it was a recurring side-game rather than the primary campaign.