Cement pots for plants do have their own share of issues, some of which are quite obvious. For one, they are quite heavy, which can be a serious issue when dealing with larger versions used to hold trees or other large plants outdoors. This can make moving them a pain, but on the bright side, it also makes them less likely to be stolen. Even medium-size planters indoors can be a bit of a chore to move. Similarly, if they are not on stable ground or are held aloft from the ground in an unstable manner, they can break if tipped over.
It should also be noted that sometimes, the planters have a chemical coating on them. According to the University of Maryland Extension, they may also contain a compound called fly ash as well as other heavy metals. This can seep into the soil. Companies rarely provide information about the compounds used in the creation of cement planters, though there is not much research on whether this might affect the plants. Consider leaving the planters outside to be rained on a few times to get some of the potentially unwanted compounds out of it.