I'm not sure of the exact amount of maintenance it requires and it's one of the factors that puts me off trying it, that and the cost.

The all-in-one coolers require no maintenance, well as much as any air cooler does.

In terms of performance they are no better than the top end air coolers but not really much worse ether and cost around the same, they don't perform as well a a custom loop but it's cheaper and hassle free.

If you can afford it the new Corsair H100 (240rad) all-in-one is very good and does beet air coolers although it costs more.

The cases mentioned here are still good for air cooling