I've hit this very problem this morning.
All my characters (certainly when they are 2"+ high) are drawn with straight line segments. Normally (like when the text is 1/2" or less tall), you dont see it, but at 2" you certainly do. Plus it makes the mill jerk as each line segment is traced out in the material.
After further investigation, you can get round it, but in my view its definitely a bug within VCarve and aspire (it sounds like aspire shares the same code base). The annoying thing is that while the 2d preview is perfect, the cut in the material is not. I've use openscam to examine the gcode output and you can clearly see the problem (see pic 1).
The fix is to convert the text to curves (right click with the text selected - Convert to curves), then vcarve as though it was text. The output is shown in (pic 2).
Its annoying in as much as the text cannot now be easily edited as its a collection of curves now - not ascii text. I suggest, copying the text with its attributes to a spare bit of your design (outside the working area) - you can always drag the copy back should you need to change it.
Its a shame that a piece of software thats used to make signs can't handle large text correctly. Still - at least there is a fix...
Hope this helps