A landmark, with tired rooms and spotty service
I stayed here for one night on the way from San Francisco to San Diego. The lobby and common areas of the hotel are beautiful and fascinating, including the many old photos in the cavernous ground floor and the various spaces -- the garden that was the old lobby, the new lobby, the giant convention rooms where the Oscars were held in the 1920s. One can wander around and absorb the bygone-ness of the place.
However, the rooms and service are also from a bygone era. Even though I upgraded to a "club room" on the club floor, which promised "all-new bedding" and other exciting perks, my stay was mediocre. The bedding was not new and was of very poor quality to begin with; the bathroom in the room was small and unattractive. The "club lounge" breakfast was one of the worst breakfasts I have ever encountered in a hotel, with just a few stale croissants, atrocious coffee, fake orange juice and a couple of slices of melon scattered about. Finally, the bellmen were full of attitude and after being not given a tip because of said attitude, became outright rude and sarcastic. 
I would definitely recommend visiting the Biltmore as part of your trip to LA, but stay elsewhere - there is much better to be had for the cost of a room at this establishment.