The whole bleeding process may take 30 minutes or less on some cars (like my Supra), but it is PITA to put the thing on in the WRX. I spent 30 minutes just trying to test-fit it. The engine bay is simply too cramped in the WRX to put the universal bleeder cap on, which involves hooking a chain underneath the brake fluid reservoir. Removing some bolts around the reservoir may help, but it is no longer a simple and fast process.
I'd probably still recommend the bleeder for other models, but it's not for the WRX.