Well, if you are talking about coilover sleeves then I would say there is no need for them, don't get them, get a good spring/shock combo instead.
If you are talking about true coilovers then the question gets more difficult.
If you are using your car solely as a daily driver, then there is no need for true coilovers IMHO. You won't be using the adjustability all that much really, and if you can find a set of springs that are the height that you like, then you don't really need the adjustability either.
If you occasionally race, then I would get a set of springs that you like (and tend towards the stiff side), and I would get adjustable shocks (Koni Yellows).
For the most part the people that get true coilovers are people that either race often, or want the ability to adjust the height without having the problems that sleeves sometimes cause.
If you are serious about racing then you have two choices. The first would be to get a good set of coilovers, preferably with adjustable shocks. Second, and this goes somewhat to what PseudoRealityX was saying, would be to get custom rate springs, and then buy Konis and ask them to revalve the shocks based on your spring rates.
Going with coilovers in this situation gives you the ability to adjust height, which allows you to corner weight the car (which won't help unless you're a pretty good driver already). That's the main thing that sets it apart from a spring/ revalved shock combo.
IMHO, for most people the expense of true coilovers is not necessary, but some people put a lot of value on being able to adjust the height, so it depends on whether being able to adjust the height is a huge factor to you. If it is not, then you'd probably be as happy with a good spring/shock combo as you would be with true coilovers.