Cleanliness:
Another advantage is cleanliness. Since you don't have to oil a belt, it will stay cleaner.
Longevity:
I don't know how valid this on is, but technically, the belt will last for more miles than a chain. I think the cost to replace a worn belt ($100) vs. the cost of a chain ($20) kind of makes this benefit a moot point.
Changing it out for a chain:
You're not locked into a belt drive system once you've designed your bike around it. It can always be converted to a chain drive if needed to overcome any of the drawbacks listed below.
Down the road changes:
The number two reason people go with chain over belt drive. With a Gates belt drive, changing your gear ratio after the fact poses a few challenges. When your bicycle is designed for a Gates belt/ring combination, it is designed with a specific chain stay length to work with that ratio. It's not as easy as just picking a new belt/ring combo off of Gates website to change your gearing, because it also has to be compatible with your chain stay length. To be concise, there's no 'after the fact' micro-adjusting your gear ratio, mostly large changes. If you settle on a different gear ratio 'after the fact' the cost to change it will be $200 or more. You will have to buy a belt and a ring to change the ratio.
With a chain drive system you can buy a $25 chain ring in any tooth size you want and install it on your bike no matter what your chain stay length is.
On the road service:
There are a few things to consider in this area. If you roll the belt, either to remove your wheel or by accident, your belt is destroyed. So, if this happens to you on a tour, you will be waiting for a new belt to be shipped to you. In one case, the belt that our customer needed was not available for several weeks. He was on tour, out of the country, so it was inconvenient. The good new is that a Rodriguez belt drive IGH bike is designed for easy removal of the rear wheel without having to loosen the belt.
Keep in mind that many IGH bikes with belt drive must have the belt loosened to remove the wheel, and then properly re-tensioned when the wheel is put back in the bike. This is a pain in the neck.
Cost:
Some people might think the cost is the number one drawback, but we've found that most people don't rule the belt drive out for cost, but for the other reasons listed above. That being said, cost is a drawback to the Gates belt drive system for many folks.
At the time of purchase, you're paying about $500 extra for your bike if it has a Gates belt drive system. This includes design requirements, a belt splitter, the belt, and the compatible rings. Cost of replacing a worn part is 400% ~ 800% greater than traditional chain drive system. Lastly in regards to cost, as I've already covered, the cost of changing your gear ratio is much, much higher.
That about wraps it up. I hope that this information has helped you decide wether the Gates belt drive system is the appropriate choice for you and your style of riding.
Thanks for reading
Dan
10/9/2015