Up-to-date with 10.10 SDK and Xcode 6. Supports OS X 10.7+.
Cleaned up and modernized code, using ARC and Autolayout.
Merged bugfixes, security fixes and some features from multiple Sparkle forks.
Truly automatic background updates (no UI at all) when user agreed to "Automatically download and install updates in the future."
Ability to mark updates as critical.
Progress and status notifications for the host app.
Name of finish_installation.app can be configured to match your app's name.

Features

True self-updating—no work required from the user.
Displays release notes to the user via WebKit.
Displays a detailed progress window to the user.
Supports authentication for installing in secure locations.
Really, really easy to install.
Uses appcasts for release information.
The user can choose to automatically download and install all updates.
Seamless integration—there's no mention of Sparkle; your icons and app name are used.
Supports Apple code signing and DSA signatures for ultra-secure updates.
Sparkle requires no code in your app, so it's trivial to upgrade or remove the module.
Optionally sends user demographic information to the server when checking for updates.
Sparkle doesn't bug the user until second launch for better first impressions.
Sparkle can install .pkg files for more complicated products.
Supports bundles, preference panes, plugins, and other non-.app software.
Supports branches due to minimum OS version requirements.
Deep delegate support to make Sparkle work exactly as you need.