iAUD has a point, in that if you don't take steps to protect access to the iDevice, you might be opening yourself to troubles. For example, if you install OpenSSH, a tweak that'll let you wirelessly get into the iPad's innards, you need to change the default Apple password else someone else can get in. The only reports about people maliciously hacking into the iDevice was because the owners of such devices did NOT change that password. So, there's that.
And yes, jail breaking does remove some of the sandbox characteristics of the iPad. Which, to be honest, is kind of the point and a good thing (IMNSHO)! I can directly attach any picture or file to an e-mail without leaving the Mail app or doing a cut-n-paste. That's a good thing. As long as you stick with a tried and true tweak, written by a developer with a good reputation (and get the tweak from a reputable source), you'll be fine. However, there are very few tweaks out there that can actually break that sandbox "wall" built by Apple.
So far, knock on wood, the iPad is just as safe as a stock iPad. In addition, should you decide, it is easily restored to stock.
But, enough of me telling you of the bennies. Grab yourself a cup of your favorite beverage and a snack and have a browse through our Hacking section, especially starting with this sticky: http://www.ipadforums.net/ipad-hacki...ed-2011-a.html
Welcome to the forum and I hope you enjoy your visit(s).