Personally speaking I find them very good, the dual battery lasts longer, and I find the extra grip with portrait shooting shutter release make portrait format shots easier, indeed I'm lost when i switch to a camera without a grip.
I also find it ballances better with a bigger lens on.
The 550d isn't the biggest camera around so if you have large hands you'll probably find it easier to hold.
best bet is try one somewhere and see if you like it.