Since the topic came up I'll put in my 2p so to speak:
Here in the UK, all of the main-line stations that I have passed through in the South East have converted to multi-coloured LED screens which show the destination of the train as well as all of the intermediate stops. The reason I was told by the staff at South Central Rwy (now Southern Rwy) that they were converting was because they were having a lot of trouble with faults, the replacement parts for the older boards (such as at Victoria and Brighton) were becoming harder to come by, and that they were upgrading the communications network to be able to handle train scheduling and announcements all in one location which meant that the Solari boards could not keep up with rapid changes.
When I first came here in 2002, they began the conversion process with the London termini (on the southern part of the network, these are primarily Victoria, London Bridge, Waterloo, and Charing Cross), then they moved on to the secondary hubs such as Gatwick Airport, East Croydon and Brighton, and finally finishing with the more suburban stations. However, at stations with only 2 platforms (up-line and down-line), they use a much older type of yellow LED board on the platform (like the red MBTA signage) wich displays the next three trains to arrive at the station. These are quite old comparitatvely (from the late 80's). Finally, at rural / halt stops, they have an 'information box' where you press a button and it plays a recorded message telling you what train is coming and when it is to arrive. These are completely un-manned stops that don't even have ticket machines at them.
The funny thing is that in Brighton and Victoria Stations, they didn't remove the Solari boards, but just turned them around so they face into what used to be the service catwalk behind the boards! In Victoria, the new boards cover the Solari ones, but in Brighton, they are hung below them. From the platform side at Brighton (when the ads are not up) you can see the board with the last trains that it displayed the weekend they converted to the LED boards!!!
-A