I haven't used carbon in over 18 years now and my tanks biological system does fine. Sure, the first week of removal might take out some "good bacteria" but this quickly multiplies over again with time.
I haven't used carbon for several years with no ill results. The only time I have used it has been temporarily to remove a medication from my tank.
On two of my filters (for a 20 gallon and 10 gallon) I removed the carbon from the commercial filter cartridge (for a penguin biowheel and a shark). I replaced this with filter floss which I occasionally change out (usually I just wring it out in used tank water and keep it as extra biological filtration). For my other filters I have never run them regularly with carbon.
I keep carbon on hand in case I need to remove something like medication (always use fresh). But I use a combination of sponges and floss in the filters.
I don't use it in any of my plant tanks..but in fairly heavily stocked, fish-only tanks I wouldn't hesitate for a minute to use it. Though, it needs to be replaced at least every week or two to remain effective(depending on how much carbon is used and how much "dissolved-organics" is present in the water).
Here is an interesting write-up on activated carbon.
