got the pro. It's performance vs the regular Javelin is about the same. It does have more bells and whistles. If those aren't important to you, save your money and buy the javelin.
For me, the advantages of the pro are a longer probe (not at all sure when that will actually matter), and the backlit display is useful.
The advantages of the javelin is the smaller size, which is a major advantage in my opinion. Also, the javelin tested slightly more accurate than the PRO - it was exactly on at 212 and 32, while the Pro was off about .5F, which isn't a big deal.
If you are left handed, the PRO would be a real advantage, as the display orients properly with the probe pointed either left or right.