Nothing really wrong with 2CR5 batteries in a functional sense, but they are expensive and have a shorter life than rechargeables. And not as commonly found in many countries.
One thing to avoid with 2CR5s in EOS bodies that use them (EOS 3, EOS 5/Elan, 1N among others)is any lens with an image stabiliser on it that takes power from the 2CR5 in the camera: it will drain the battery very quickly. Not as commonly reported now with more modern reserved lenses, but the major culprit I am aware of is Canon's old 75-300mm IS tele lens (around 1995; still common on the second hand market). Other pricier lenses in the L-series range are a bit easier on power but image stabilisation will still tax a 2CR5, hence many cameras use or offer alternative power sources, like the power drive booster (8 AA alkaline or AA lithium).