Aslan, for many of us this is not a minor expense. There can be other expenses like library, software, computer equipment, meals on the road that aren't comped, and tips, but typically these will be relatively minor.
For a Schedule C filer, since rooms and meals if paid for in cash would be business expenses, such comped items will be a wash. I have not heard that the IRS has ever asserted that comped rooms or meals are reportable as income, either by Schedule C filers or by others. (And I've been paying close attention to everything other players report on this subject on public boards and elsewhere.) For one thing, there would be a obvious, difficult valuation problem. Actually, were the casino instead to give you cash that you used to pay for meals, it wouldn't be 100% a wash, even for a Schedule C filer, because meals are a special category of business expense that isn't 100% deductible. Fortunately, the tax boys have never made an issue of meals written off by the casino as a straight comp.
I assure you that the tax laws treat comps in the form of CASH BACK, and other comped goods or prizes of substantial value, as taxable income. This is true whether or not you file Schedule C.