This was the announcement I kind of expected for E3 but close enough. The word is Gaikai has the stronger network compared to Onlive but that can change. Makes me wonder if Onlive just didn't want to sell or was too expensive.
The money seems big now, really big considering where Sony is financially, but they are making a pretty safe deal considering where media in general is heading. Add that they also bought a customer base that's creating revenue now (over 10 million at end of 2011 says a quick search), the future customers in the Samsung smart TV deal, and 388 million isn't so much. This also seems early enough that it gets integrated into whatever hardware and network the PS4 will be using. My biggest surprise is that Sony is doing this before anyone else, console wise.