Moving to London where the water is very hard compared to my previous home, I was in desperate need of a water filter. The Brita Marella did a great job, all I did was open the lid fill it up with water, let the water filter through slowly (and even then it didn't take too long) and I could already taste the difference in the water! It was not remotely chalky, it tasted better (basically it didn't taste chalky), my tea tasted better (that's right I poured my filtered water into the kettle) and my kettle didn't have nearly so much limescale as before! This water filter only needed refilling once a day as it holds enough water to fulfill your daily requirements.
Buying this water filter in areas with hard water where it usually seems a better choice to buy mineral water will certainly save you a lot of hassle and money, because the filtered water tastes so good you can forget those regular trips to the shop and lugging back expensive heavy bottles of water! I'd highly recommend it as it's easy to use, looks good and filters out some great tasting, clean water.
You could argue it's a hassle having to buy extra filters time to time to keep the Marella working, but it's worth it as the filter doesn't have to be changed often.