If you ride in rain, and wash off chain lubricant; or ride at high speeds, requiring more lubricant, you can now quickly re-oil the chain to compensate. Also, you no longer have to fear the oiler losing prime and running the chain dry with a reservoir full of oil. After refilling the reservoir repriming is simply the push of a button.
I have found manually pushing a button a few times during a rally, nor cleaning up a little oil spray off the rear end, to be of little inconvenience to gain the assurance of having the chain lubricated. What was an inconvenience was to find my chain bone dry, squeaking, kinking, and close to failure during the Iron Butt because the oiler I was using stopped working.
On a recent 11,000 mile ride I had a chance to field test the HawkeOiler at length. I found it was easy to control the normal oil over spray you get from an automatic oiler when excess oil is thrown off the chain. To do this I simply oiled the chain only when I would be moving at reduced speeds inside the city speed limit areas. This gave the oil a chance to distribute itself before seeing higher centrifugal forces.