Despite repeated attempts with various fonts and settings, I find that font rendering in the final .SWF is inconsistent, often exhibiting spaced-out kerning/tracking. Line breaks in the original Captivate document are sometimes ignored and changed in the final .SWF.
Some fonts are ragged when used for one purpose, and smooth in others. I have enable the transparent caption smoothing option. For example, the question number on a question slide renders beautifully, but the same font/point size is rough as a caption.
A few things I've tangled with and might save you grief.
1) If dealing with slides using bullets, the ones with them will appear different than the ones without if using the Transparent caption
2) Make sure and avoid copy and pasting from Word to Captivate. MS still has the bad habit of inserting evil invisible gremlin characters. I like to paste into notepad then Captivate and then format it.
3. Play around with the quality settings in your publish, I found that setting to high did increase size some, but made certain fonts much cleaner
4. Experiment with different fonts and find ones that are reliably consistent.
Hope this helps, and keep fighting, the community here is very helpful.