I just happen to check out the page about Impulse Reactor today, and it seems like Sins isn't using any of these except the anti-piracy and maybe also the IRC channel.  I'm pretty sure the Sins achievements are just stored on the local machine, multiplayer is done through Ironclad online (which is fine, but the integration of Reactor sounds better), and I didn't know Impulse had an overlay similar to Steam.  

• Multiplayer Matchmaking. Impulse Reactor includes built in support for intelligent match-making. Based on the Elo rating algorithm (http://en.wikipedia.org/wiki/Elo_rating_system) a developer can literally just send a user off for multiplayer and get a user with a similar skill back. This works even if the players purchased their game from a third-party service (Impulse Reactor is vendor neutral).
   
• Rankings & Achievements. Impulse Reactor has built in support for rankings and achievements. To ease support of implementation, Impulse Reactor supports sending and receiving data in XML. This means developers can implement their achievements in a platform neutral way and support multiple achievement platforms at once.
   
• Community Features. Impulse Reactor includes the Impulse Overlay which provides a standardized way for users to find friends, chat online, check out rankings and more. However, developers can easily make use of these features as well since (to stress this: Impulse Reactor is server based, not client based). This means a developer could, for instance, create their own IRC client within their game with only a few lines of code or integrate friends, groups, invites, etc. into their game natively without having to re-distribute a third-party client. Even the overlay features are skinnable to match your game's look and feel.