This is commonly called Guk Po Cha (pronounced gook po cha) and it has an interesting flavour. If you buy your mums from a Chinese herb shop they will be very flavourful and quite small and will steep well. In most recipes, there are a relatively small amount of mums to the pu-erh pot. Chado (www.chadotea.com
)in LA sells a nice blend that is smooth and inexpensive.
I wouldn't use your very best pu-erh to blend since the mum flavour is pronounced.
Crysanthmum has a cooling effect and is good for internal heat conditions (Chinese medicine). It's more likely satisfying in the heat of the summer.
I've seen a great deal more of it ordered with dim sum in the warmer months.