It really depends on your situation and preferences. As mentioned, it's common for some to use CCA to bring rental income down to zero so no additional tax is due (keep in mind CCA can not be used to create or enhance a loss). The trick is to keep in mind that typically speaking (assuming the property has at least held its value, if not gone up) when you sell, you'll have to repay any CCA as 'recapture' in addition to any capital gains on the property. This becomes more and more true the longer you've held the property. IE, a $1000 CCA for 20 years would then result in a $20,000 recapture added to your bill.
The other thing to keep in mind is the different tax rates. If you're one of the lucky folks who is always in the highest tax bracket, this doesn't really matter to you. But for those of more moderate tax situations, you may find yourself using CCA to reduce low-mid tax rates, but when you sell and all that CCA gets recaptured as well as your capital gains, you may find yourself having saved mid-level tax for years, and repaying high level tax.
As much as it isn't fun leaving possible tax deductions on the table, there's definately an arguement for NOT claiming CCA. All depends on your personal situation.