Payoff mortgage on rental

[RG Mullen]

I am a conservative investor who has a good income and good liquidity. I have a rental home that is getting into a range where I can pay it off this coming year. The benefits to this are:
-less debt
-increased cash flow (at the expense of liquidity)
-interest savings on mortgage
Beyond simple issues like opportunity costs, are there tangible disadvantages to paying off a rental house? Will I be taxed on all of my rental income if I do this or is there a way I can do a charge back for the money I contributed to pay the mortgage off? That is one of my major concerns but I am interested in any other issues I might have missed.