I find no reason to JB my iPad, but have a JB iPhone 3G. I did the iPhone simply because I wanted to tether it to the iPad.
If the multi-tasking is really important to you, the JB is what you need to do (at least until iOS 4 arrives). The downside to JB is there can be problems in the process and you have to restore your iPad.... there is little danger you would actually "brick" you iPad... Also, a JB iPad getting unauthorized apps is also open to virus/spyware, and very poorly written app issues, with zero quality control......
Here is a forum with lot's of info about JB/Hacking your iPad
http://www.ipadforums.net/ipad-hacking/
So you weigh the pluses and minuses and decide for yourself
I don't see the need for me, but I am not you.....