I use the arrow keys all the time to move my objects; however, sometimes the nudge is a bit too much.  So I might turn off the Snap to Grid feature (instructions below).

But, even easier is to hold down CTRL and press the ARROW keys to nudge the freeform in 1-pixel increments.  This is one screen pixel.  What 1 screen pixel represents is relative to the document area depends on the zoom percentage.  When your document is zoomed in to 400%, 1 screen pixel is a relatively small nudge distance on the document.  When your document is zoomed out to 25%, 1 screen pixel is a relatively large nudge distance on the document.

 To Nudge:

1. Select the object and then use the appropriate arrow key.
2. Each key press will move the object approximately 1/12 of an inch.
   PowerPoint applies this predefined amount when the grid is enabled.

To Change or Disable Snap to Grid Settings:

Office 97 – 2003

1. Click Draw on the Drawing toolbar and choose Grid And Guides.
2. In the resulting dialog box, you can select or deselect the Snap Objects To Grid check box, adjust the grid spacing, and display the grid and/or drawing guides on your slides.

Office 2007

1. Under SmartArt Tools, Drawing Tool, Picture Tools, Chart Tools, etc., on the Format tab, click Arrange, and then click Align.  If you are working with a Table, select the Layout tab in the Table Tools Ribbon.
2. Click Grid settings, and then clear the Snap objects to grid check box or change the number in the Spacing box under Grid settings.
   If you do not see the SmartArt/Drawing/Picture Tools or Format tabs, make sure that you selected an object.

Remember, for a quick, small nudge is CTRL + ARROW key!