What kind of sensitive info is gonna go through cydia? Honestly the only way your stuff can be remotely compromised is if you have open SSH turned on, and you don't change the password/leave it on all the time.
So you are going to jailbreak a device meant for business? I'd recommend against it lest you possibly be fired. 🙂
As for your original question, Cydia is safe, so long as you trust the repositories you add to it. The defaults are well known (iSpazio, BigBoss, etc) and tend to be more reputable.