Worth the investment when you're putting the bike into storage for anything more than 2-3 weeks. Ethanol left sitting causes a phenomenon known as phase separation where basically (in short) you end up with water in your fuel.
On smaller 2 stroke engines this is a BIG issue since the fuel is also the carrier for the lubrication oil, and a single droplet of water along with the fuel/lubrication oil mix can wash the lubrication oil off a surface and result in a bearing score or a ring scoring a cylinder wall. 2 stroke engines are often attached to things that don't get frequent use - snowblowers, weed eaters, lawnmowers, etc. When left sitting, particularly in an enclosed space with large temperature swings (garage/shed/etc) where heat and cool cycles draw already moisture laden air into and out of the gas tank, phase separation becomes a bigger issue with ethanol laden gas that is known for phase separation.
However, on a 4 stroke engine where the oil is more robust, the oil lubrication system is pressized, the oil is not mixed with the fuel, and (in the case of many motor vehicles) the engine doesn't sit for more than a day or three before being driven... there is less of an issue with a small amount of water in the fuel. I'm not suggesting that it's a good thing, but it won't cause nearly instantaneous damage either like it almost always does on a 2 stroke.
So, it's never a bad idea to use ethanol free, but for 4 stroke engines as pretty much all street bikes are equipped with, it's really not necessarily worth the investment UNLESS the engine calls for high octane fuel and you just happen to get non ethanol along with it since some premium fuels (aforementioned Shell, for example) are no ethanol.
