I can actually admire their willingness not to accept a cease & desist letter lying down, and to actually fight for their business model.
Essentially, Psystar was trying to get the courts to question Apple's ability to enforce concepts written in their EULAs, including the assertion that all retail copies of Mac OSX were only "upgrade editions" (despite not saying that anywhere on their boxes).
Basically, that's been Apple's defense/excuse for why it's illegal to BUY an OS X installation CD or DVD and proceed to install it on generic hardware of one's choosing. Theoretically, the ONLY way to purchase an initial "full install" OS X license is by purchasing a new Apple Mac computer that comes with it.
Everything else they've done to prevent such a disc from installing and working on non-Apple branded hardware was done artificially. (Their machines contain the same Intel architecture as any other PC clone.) So it was at least a *possibility* that one could succeed in arguing in the courtroom that these measures were anti-competitive moves on Apple's part. (After all, if you PAID Apple for the operating system disc, it's not like you "pirated" their software. You're simply trying to BUY their software but use it on alternate hardware, vs. being artificially coerced into buying the Apple hardware to go with it, right?)
But IMO, none of these "anti competitive" arguments would hold any water unless you got courts to agree first that there was no real basis for claiming the retail purchased OS X discs were in fact simply "upgrade editions, not for use for a new, full OS X installation".