Android 5.0 brought major changes to the platform, and that made it hard to get the Xposed system tweaking framework functional. The project's developer has finally announced that Xposed for Lollipop is ready after months of betas and unofficial builds. That doesn't mean it's completely without risks, but nothing should be obviously broken.
Installing Xposed is a little more involved on Lollipop than it was on KitKat. You'll need a custom recovery to manually flash the Xposed framework, then you can install the APK for managing modules. Just make sure you grab the right ZIP file for SDK 21 (5.0) or 22 (5.1) and system architecture (x86, ARM, or ARM 64).
Once you're up and running, Xposed can be used to make software mods to your device that make it more capable. It's generally easier than installing a custom ROM and works on most devices. There are two incompatibilities right now. Samsung's changes to ART can result in a bootloop on devices running the standard TouchWiz ROM. However, there are some unofficial Xposed builds that can get around this. Some Sony ROMs also have bugs that cause fatal errors that cannot be fixed simply by uninstalling Xposed. So flash with caution.