I always find it interesting that they are sold as xmas tree "rocks," rather than "corals with worms," or some such. It's a wonderful thing to see, and I would guess that few of the worms or corals are sold to people who understand their care.
I agree with both OG and PH.
One small elaboration. While it is true that porites is an "SPS," it is one of the hardier of the group. If you are successfully keeping stony corals, then this one should not be a problem. If you are not set up for stony corals, then don't try it.
The biggest problem I have with the whole thing is that these are parts of coral heads that have been whacked off the reef. As a diver, I feel terribly guilty when I even touch the reef. As an aquarist, I have made a point of purchasing or trading for tank-raised frags.
Anyway, if you're not set up for stonies, pass it up. It would be worth a try if you have succeeded with frags (which tend to be more forgiving).
Inland Aquatics has some captive-reared porites if you want to try your hand.