I wanna stand up for the CAE, I can understand why people have so many bad experiences with them, they are so often bunched in with the 'tank cleaners' by the LFS, they are pence to buy and IMO pretty fish when they are small. They must be one of the most abundantly mis-sold fish in the industry.
My friend bought three for his tank the other day he is very new to the hobby and was totally wrongly informed, he was told they were SAE not CAE, that they were less problematic than gibs because of size and mess and that they were totally community! He won't take them back at the moment and thought I was being dramatic when I told him he would have probs. He will probably be fine for a year.
I have two CAE in two different tanks, In the right tank I think that they can have a lot of character, I keep my gold 6" CAE in a tank with a Jewel Cichlid and a very aggressive 7" clawed shrimp they all work well together and he has never even been fin nipped he seems very hardy and is still a very profficient tank cleaner but when he was in a community tank he was a nightmare.
the other CAE I am baby sitting whist my buddy goes travelling. he is natural colours, much smaller and was a pain until i did a shuffle around and put him with middle and upper level fish now he seems fine but I'm glad he will be going back soon because I think he would become a problem.
Never keep them with frogs (ACFs or ADFs) they love their slime.
I think that the pros are that they are very hardy, lot of character, pretty when young, a 'tank cleaner' that will be seen by day, and can live along side very aggressive tank mates if big enough.
Cons- Get mis-sold and are often one of the first 'tank cleaners' people buy, not good with other bottom dwellers, opportunist feeders on sick fish and not so pretty when older... My housemate has nicknamed my golden CAE 'Penis fish' and I cant really defend it!!!!