Arguably, Microsoft is known to be leveraging about 310 patents for this. There's a decent likelihood that at least a decent number of them are legitimate under current law (your views on where software patents should be aside). They may be able to defeat specific patents, individually, but that burden would be on them. Whereas the wholesale deal from Microsoft covers them from the legit ones and the illegit ones in the pile for probably an overall bargain.

It's probably pretty unlikely even most of the 310 claims would be seen as "bogus". Under current law.