To start, you now have achievements that tell you how close you are to hitting the goals you need to reach the affiliate or partner levels, such as the number of times you stream in a given period and your typical viewer count. Twitch will also give you a statistical summary after every stream, so you'll know which achievements you've reached, where your traffic is coming from and other data that can help you grow your audience. If your viewership spikes every time you play Playerunknown's Battlegrounds, you won't need to dig up that data the hard way.
Twitch is also making a much bigger deal of "rituals" -- that is, those everyday occurrences in the life of a regular streamer. There's now a formal "/raid" command that automatically hosts another channel and drives your viewers there, so it's easy to show affection for a fellow streamer once your own stream is wrapping up for the day. There are even raid stats and moderation tools to help you identify where that flood of new viewers is coming from and thwart pranksters. If there's a new user, they can let everyone know and get a special welcome. You can offer "premieres" where you host the viewing of a pre-recorded series (say, a "let's play" for a new game). And in a not-so-subtle attempt to challenge Discord, there will be always-available chat rooms that let viewers discuss topics without cluttering the main feed.
And yes, there's an improvement for viewers: you can finally gift subscriptions. If you have a friend who can't afford to subscribe or you're just feeling generous, you can give someone a month of access to any subscription-enabled channel at any tier level ($5, $10 or $25). This won't auto-renew, but it can be helpful if you want someone to participate in a subscribers-only event or just help them use a favorite emote. Streamers can use this to hand out prizes, for that matter.
These features aren't available right away. You'll have to wait until November for achievements, summaries, raids and welcomes for new users. Premieres, rooms and gifting are due sometime in the fourth quarter of the year. All told, though, it's clear that Twitch knows its success hinges around convincing people to stream regularly. The more likely you are to make money from your stream and reward viewership, the more likely you are to attract a big audience -- and that, in turn, could help Twitch compete against livestreaming services like YouTube and Microsoft's Mixer.