Here's how it's done:
- Press the Menu button and select Settings.
- Tap Applications, then Manage applications.
- It may take a moment for the list of applications to display but once it does, select HTC Sense.
- Scroll down a bit and tap the "Clear defaults" and "Force stop" buttons. A window will pop up asking you to confirm that you want to stop the application. Tap OK. Note: Force stop is optional.
- Now press the Home button.
- Select Launcher from the pop-up window.
- If you want to use the standard Android Launcher instead of Sense whenever you press the Home button, press the "Use by default for this action" checkbox.
I've got some side-by-side screenshots (Sense on the left, Launcher on the right) below.