I've spent a bit of time looking for just such a thing, and was unable to find one I thought was right for the job. I tried out several demos and was dissapointed with each. That was about a year ago. I am a graphic designer and have a lot of financial clients, so I've made a ton of graphs. Some tips on using PPT
I use excel for bar charts, it makes better ones than PPT, choose no line for data bars (makes color changing easier)
don't use excel or PPT for circles - they look cruddy. I use Adobe Illustrator for Pie charts and 3D pie charts. There is a charting tool in it. Then copy into PowerPoint.
If the presentation is slick enough, people don't think "Oh, PowerPoint" they think "Wow, slick" - One way I achieve this is to take apart the graphs and make adjustments, especially color as the excel colors are ugly, ungroup the chart, twice, maybe more depending on how it comes apart, and modify the colors. If you later want to animate the Pieces you can or pyou can group them and animate. After you make your changes, re-group the entire thing, so you don't accidentally knock part out of whack.
It really helps to have custom toolbars here. I add a lot of drawing tools like align and distribute horizontally and group and ungroup and such, to the standard PPT interface it makes it much easier.
One thing on working with graphs is the number of small items you end up with, keep in mind that the selection rectangle selects anything it touches, so for example if you want to group all the left axis numbers (which I almost always do, and choose right align) just click a little outside of it and drag the rectangle down the edge of the entire row, that selects them all and then you can group them so they stay together and can be moved easy and moved back easy.
Good luck.