I dont use the Merchant part of Jamba.
I dont use the Macro part, but can understand others do.

I do use the quest part.
I do use the item bar, i think its great.
I do use the procs, but maybe a way to import/export the list of available procs would make it easier to add them and share them. Now i have to wait for a proc, look up the spell id and add it.
I do use the taxi part.
Chat is cool too.