There are no major concerns, but there are a few things you should be aware of. Chunks of cedar will not break down as quickly as shredded bark. This makes it an excellent choice for use around shrubs and trees, where it will be left undisturbed for years. It works somewhat less well in perennial beds, where you frequently may have to do some maintenance, such as dividing or moving plants. But it is still a good choice. For both cedar chunks and shredded bark, be aware that if you work them into the soil, you may have to add extra nitrogen to aid in their decomposition.
Because the cedar chunks will not form as dense a layer as shredded bark, you can make your mulch layer somewhat deeper, which means you will need more for the same coverage. Also, because cedar chunks are lighter, there is a greater likelihood that they will get blown out of your beds.
Here is a yard and garden brief on mulching:
http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h139mulch.html
