It's worth it if you need to access the internet anywhere you go. If you need email all the time. If you need constant access to your data. It's worth it. I use anywhere from 2.5 to 3.5 Gigabytes on my device alone. $30 is an extremely small price to pay for this constant reliable access.
RIM is awesome because I get my emails within 30 seconds of it being delivered to my inbox. This is paramount to the side business I run. Time is money.
So it's up to you if it's worth it or not. How much you use it will determine that. If you rarely need to access the net while away from home, or if you don't need your email on a NOW basis, then you might not find it very valuable.
well said....kudos to you