Those ray guards are a nice product, but it's a trade off, IMHO.
If you wear the ray-guards:
pros: Piece of mind (a very important factor that only you can judge) & ADDED protection (these things ARE NOT 100 % ray proof, I've seen guys hit while wearing them).
con: I've found these boots to be very uncomfortable & heavy, especially in mud.
Even if you have the guards, you still need to shuffle your feet to avoid rays. If you still have to shuffle your feet, I feel you might as well wear a boot that is more comfortable ( I recently switched to Simms from the foreverlast & DAMN they are comfortable). If your boot is more comfortable, you will stay in the water longer, wade longer, & cover more water (which equals more fish). As we all know, that's all that reallly matters.

Just my two cents.