Indeed.
I had to wipe all remnants of Yosemite off my External HD's Unplug all unnecessary peripherals, basically reduce my Mac Mini to OEM state. Those who's Macs shipped with and was bought with Mavericks may choose to do what I did without a Genius Appointment. Remember Internet Recovery! Here's my procedure I used to put me back in out-of-box state. Back up all of your Data!! Know the procedure for NPRAM and SMC reset for your Mac Model!!
1. Make sure you only have your original Mac equipment installed. A Wi-Fi connection ready is recommended. Wi-Fi is stable during this process, imagine that!
2. From Shutdown, Power up holding Command+R
3. Enter Disk Utility and make two single passes of Zeros across your entire internal HD. 1 single partition. Title it "Macintosh HD" this will take some time. The positive. Zeros will recover lost HD space and remove all traces of data remnants.
4. Quit Disk Utility and shutdown.
5. Power up holding Command+Option+P+R. Keep holding until computer restarts then release keys. The Mac will boot to a flashing "?" folder. This is the NPRAM reset.
5. Shutdown. Now do an SMC reset of your Mac. (Mine for Mac Mini is to Shutdown. Unplug power. Hold power button for 15 secs. Wait 5 secs and plug power back up.)
6. Hold down Command+R and power up. Your Mac will request an Internet Connection. Connect. It will download the Internet Recovery.
6. Select "Reinstall OS X" from the menu. It will download the components needed to install the OS X. Follow installation prompts.
Please be aware that this procedure will install the OS X that shipped with your Mac. If you bought your Mac with Mavericks installed. Internet Recovery will install Mavericks. If your Mac shipped with Mountain Lion or Lion, Internet Recovery will install what shipped with your unit. For some of you, this is the frustration. However, it's best to revert back to your known good OS X and wait for Yosemite to come out of Testing and Beta updates. For now, let your Mac be a computer and iOS remain mobile. This procedure, it is my hope, will keep some of you from making an unnecessary trip to a "Genius" appointment.