Joco,
The big thing is that the packs you are used to are Nicd's, and you bought a Nimh pack which has a power density of about 2-3 times a typical Nicd pack, so although you bought one with higher current capacity, it is also smaller.
Have fun with it and if you are used to cycling your Nicd's every month, only do it every three with the Nimh.
Curtis