Graph Utils (Open-Source)

Hi List, Anyone out there using something other than rrdtool for creating graphs?? I have a project that will need a trend taken, and unfortunately rrdtool doesn't fit the bill. All of the scripting, data collection, database archival, etc will be custom written or is already done (with some hacks of course :). So really what i'm looking for is something along the lines of GNUplot. Has anyone used it before and would like to share experiences?? Seems like it will be able to my plot data accordingly, but wanted to see if there were any other popular tools I've yet to come across. (Open-Source only please) TIA, M