PS4 2.0, codenamed Masamune has been so far a mess with numerous bugs causing more issues than any good the addition of features could do to date. Sony seems to have realized that, and 2.01 is being rushed out to deal with some of the worst of it.
In particular Sony has said that 2.01 will deal with the Rest Mode issue. Replacing the standby feature, Rest Mode has been causing numerous issues where PS4’s that are suspended cannot be woken from stasis again. People were actively avoiding using the feature so that they wouldn’t have to deal with the bugs that could make it difficult to get the PS4 working properly again and it had become the poster child of 2.00 issues.
There have been other issues with the Masamune update – namely people being unable to connect to the Playstation Network and some releases experiencing trouble (such as Evolve Alpha). Sony has not said this one will address those issues but given they got less press, they may be trying to fix it on the QT.
Version 2.01 is being released throughout the day today as Sony appears to be trying to avoid crashing things by patching everyone at once. If you want to get the update and make it come quicker, you can go to Settings -> System Software Update and get it to update for you.
Oddly this information is not found on their facebook page or in the main regions of their site, nor is any information about 2.0. To find information regarding it on the Sony website you have to go to their forums where they link to twitter where they announced this. Assuming there are no further major hiccups, one imagines that the PS4 FAQ will be updated shortly to talk about ‘what is PS4 2.0’ instead of the current ‘what is PS4 1.7’ section that there is.