I think the PS4 may be stuck trying to upload saves after the firmware upgrade, from what I have been reading that is what the flashing yellow light is (it uploads and unsent saves every time it is put into rest mode). As you can see from my original post I noticed and my saves were not uploading due to PSN saying "not enough upload space".
I have have deleted some old uploaded saves (from games I have traded in or not going to play again), manually uploaded the saves I wanted and now it seems to work, it blinks for a few seconds whilst it uploads, then goes constant yellow.
I would advise anyone with the rest mode problem to check the notifications to see if there is a problem with the save uploads.
I have little doubt be above is probably caused my some PSN server problems as it has been so temperamental.
Just thought I would share some problems my PS4 has has since V2.0 to see if there are any other duders experiencing the same problems.
1) Console sometimes will not come back on from rest mode - no matter what I try, even holding the power button will not switch it on will not make it boot, I have to unplug the console, wait and plug it back in.
2) Save game uploads failing saying "Online Storage Full" - really weird, I have had to delete some older save files to upload recent saves - this only has happened since V2.0
I never really got into it for some reason, it just never connected with me, I think it stems from the fact that I visit the site on a daily basis watching and listening to almost all the content so I already know all the games the team recommend.
The Room games are a must. Cant believe I am saying this but the new Angry Birds Transformers is good (not like an Angry Birds game at all), Marvel puzzle quest and Terra Battle (from the famous Mistwaker studios) are very good too. Honorary mention to Star Command too.