Hangouts was horrible to me for just one reason - on the smartphone, it hid info on who is online right now.. perhaps this was designed to motivate us to send more messages, but it meant i could no longer easily know if someone might answer now, or if i better try sms/call/.. and then as of recently, Hangouts just fails to notify me of messages, or keeps re-notifying me of old ones, and now i barely use it any more.
Google+ had a similar design decision, when it showed (don't know if this changed) friend suggestions without indicating if those people actually use Google+, or if your adding them to a circle will just spam them to join a social network they don't (want to) use. it's understandable that Google might want to do these things to grow their platforms, but without tact and understanding for what the users really want, they're achieving the opposite.