NEW YORK ( TheStreet) -- As always seems to be the case, Apple ( AAPL) had an enormously busy week, both in the stores and in its stock. Apple rolled out its 128 GB iPad earlier this week, pushing the model toward enterprise users, artists and educators. "With twice the storage capacity and an unparalleled selection of over 300,000 native iPad apps, enterprises, educators and artists have even more reasons to use iPad for all their business and personal needs," Philip Schiller, Apple's senior vice president of worldwide marketing, said in the press release. With the success of the iPad, PC sales have slowed, and people are turning increasingly to tablets for their needs. Research firm Canalys has taken note of that trend, and is now incorporating tablets into PC sales, thus making Apple the world's largest seller of PCs. Canalys says that one-in-six PCs shipped in the fourth quarter of 2012 was an iPad, with Apple selling 22.9 million iPads (many of these were iPad minis, according to Canalys) during the period. Apple also sold 4.1 million Macs. It's not all roses for Apple, though, as the stock has come under pressure in recent months, leading one activist shareholder to call the company out. Greenlight Capital's David Einhorn has sued Apple, asking fellow shareholders to block Apple's proposal to get rid of preferred stock, which he says restricts "the Board's ability to unlock the value on Apple's balance sheet." Einhorn's a Hustler and He Doesn't Understand Or Care About Apple "We believe Apple must examine all of its options to unlock the growing value of its balance sheet for all shareholders," said Einhorn, in a press release. "Over the past several months, we have had an ongoing dialogue with Apple regarding one option to do so, namely the creation of a new security, a perpetual preferred stock that would be distributed at no cost to Apple's existing shareholders, and would provide an attractive, sustainable dividend while preserving Apple's financial resources to pursue its business strategy." Apple issued a statement responding to Einhorn's letter, saying it will "thoroughly evaluate Greenlight Capital's current proposal to issue some form of preferred stock. We welcome Greenlight's views and the views of all of our shareholders." Shares of Apple closed out the week 4.71% higher, to finish at $474.98.