I've streamed a bit in the past, did a full Dark Souls playthrough om stream together with machomuu. Had some people that'd join me regularly to watch my progress. I'd say it definitely somewhat added to the gaming experience, not so much to the game though. Also beware of people who like to do backseat gaming, because that in turn might ruin the experience.
One thing I've noticed about streaming is that it can become very tiring, having to split your attention to your audience and having to interact with more than just the game. I'd also say that (depending on what your reasons for streaming are) you shouldn't care too much about setting a goal for hitting a certain amount of viewers and/or followers, because that can easily drag your motivation down and make it a pretty bad experience alltogether when you don't meet the goals you've set.
Regarding viewing, it really depends on the streamer really. I've only been subscribed twice in total. I noticed that I generally favor the streamers that have interaction with audience than to the streamers that haven't. I'm not saying those streamer are bad, but I don't see a reason to watch a livestream if the streamer isn't trying to pull in their audience. Currently I don't watch any streams regularly, though.
I'd also like to highlight Sp4zie, not sure if there's more people out here that know him, but I've been a fan of him for a while now (even rocking that merchandise (a nice rubber bracelet)) but I don't actually ever watch the streams. I'm way more fan of just watching the stream highlights and youtube content at my own leisure.