charge coolers were good in the early days when the cars were new and nobody wanted to make major mods to the car to fit big front mount intercoolers.. however, the cars are generally making much more power than they were 10 years ago and the charge coolers just can not reject the heat at the same rate that the turbo makes it.The net result is the water gradually running hotter and hotter.The other problem (apart from cost) is pump reliability- once the pump stops you are in serious danger of detonating the engine.
There also have been many problems with chargecoolers leaking water on high boost cars.
Lotus used a charge cooler on the Esprit simply because it is a mid-engined car and it was very inconvenient to use an air to air cooler...
simplicity is always best in our opinion.