Both cases claim that Sony has made features consumers paid for "inoperable" with the release of firmware version 3.21. The firmware update is "voluntary," but those that do not cannot sign into the PlayStation Network, or play their games online.
Both suits also state that Sony did not properly disclose that they reserved the right to remove built-in features, and that any removal of the "OtherOS" feature was not disclosed in the PS3 TOS, or SSLA (System Software License Agreement).
The second suit specifically says plaintiffs "lost money by purchasing a PS3 without receiving the benefit of their bargain because the product is not what it was claimed to be - a game console that would provide both the Other OS feature and gaming functions."
The class action suits include anyone who purchased the PS3 console between November 17th, 2006 and March 27th, 2010.
IGN has the full PDFs of the filings, here: Todd Densmore v. Sony and Antal Herz v. Sony