See for yourself. If you're willing to shell out $150, you can purchase the entirety of The Beatles' official catalogue through iTunes ("All the studio albums, the Past Masters collection, all A and B sides plus plenty of liner notes, photos and documentaries courtesy of the iTunes LP format"). Or, if you prefer a more piecemeal approach, you can acquire their songs and albums one-by-one. Both are options now.
Here's Apple's press release for the announcement, and here's a New York Times report with more details.
Excerpt (from the latter):
While getting access to the Beatles catalog has plenty of symbolic significance, it is unlikely to bolster Apple’s bottom line.
For all the success of Apple in becoming the largest distributor of music on the Internet, the iTunes store is not a major source of profits for the company. Apple executives have said that iTunes is roughly a “break-even” operation.
“The music itself is a vehicle to allow them to sell more iPods and iPhones, which is where they make real money,” Mr. Bajarin said.
And despite the deal’s symbolism, its financial value for the Beatles is uncertain. About three-quarters of all albums sold in the United States are still CDs, and physical albums remain far more profitable for record companies than downloads.
Mr. Jobs has tried to make a deal with EMI and the Beatles many times before, but negotiations have always broken down, usually accompanied by a flurry of online rumors, accusations and conspiracy theories. Further complicating the relationship between the parties, Apple Corps, the Beatles’ company, and Apple, the computer company, had been embroiled for decades over trademark disputes.
In the past, Paul McCartney has said that a deal for Beatles’ downloads would have to be approved by all the band members or their heirs.