Of course multiple groups can present problems. Since the Contact folder will list all Groups in alphabetical order, along with Contact names, finding the group can be a problem. Having to scroll down the Contact list to get to your WORK group could take a while.
In my research I stumbled across an excellent idea. When you name your group, put an asterick, parenthesis, apostrophy or other symbol at the beginning of the group name (i.e. *Work). The Contact folder lists symbols before letters so all of your Groups will be at the top of the list, very easy to find. Additionally, use of different symbols will serve to prioritize your Groups on the list. On my 8300 with default text I have room for 11 groups at the top of the Contact list before having to scroll down. That should be enough for most folks.
It isn't a second phone book but it sure makes accessing the groups a lot faster.
Hope this helps.