In reply to sjc and others: It is now dated but this excellent BMC article on belay devices is still worth a read
http://www.thebmc.co.uk/modules/article.aspx?id=1436
The basic conclusion it draws is that Sticht plates (especially unsprung ones) and ATCs are essentially very different style of belay device but at the time the article was written, that both still had their uses and their place.
A quick bit of history. Prior to 1987 the only options for belaying where pretty much a body/shoulder belay, a figure 8, a Munter/Italian hitch or a Sticht plate. Then Lowe Alpine invented the Tuber, the first 'tube style' belay device which offered very slick belaying.
In the late 1980s climbing had become a lot more athletic and fluid due to more people climbing indoors and climbing sport routes rather than just 'ledge shuffling' on lower grade trad routes outdoors. As such, the requirement for belay devices to smoothly feed out rope had become increasing important to those climbing at all grades. A more fluid style of climbing also meant it was generally easier for belayers to remain attentive which further reduced the need for a 'grabby' belay device. The result of this was almost a wholesale move towards, first the Lowe Tuber and then to its successor the Black Diamond ATC.
However, this shift to 'slick' belay deivces had downsides in that they lack 'holding power' when belaying heavier climbers or abseiling on thin ropes. Numerous attempt to solve this issue were made over the years with devices such as the original Tuber and later Wild Country's Variable Controller offering two belaying modes. These attempts were generally inconclusive and not universally liked and it took until the last decade before the solution of 'grooves' was settled upon by the majority of manufacturers as the best way to increase holding power of slick belay devices.
The upshot of this is that we FINALLY now have numerous belay devices that offer a good (if not perfect) mix of slickness when feeding rope but sufficient holding power in the case of falls or when abseiling. As such, I think that where as ten years ago you could very plausibly argue that sprung Sticht plates were still a good belay device for novices we are now in a position where they can and should be consigned to the status of historical curiosities.