Another vote for Apeks here!
For me they are the dogs Bollock*.
They are propper cold water regs designed to be used and abused. They are also well designed and easy to service and set-up after a service.
Their design is also one of the more modern designs, and in terms of effectiveness, their dry sealing system is about the best, as it keeps the internals DRY (rather than bathing them in any oil or anything)
There was a very nice article in the last issue of the UK magasine 'Diver' this month, where they were talking about the differences between different cold water anti freezing technology. (basically, Scubapro say that you want as much water flowing over the insides of the first stage as possible, and the rest of the diving world say to keep the water as far away from the workings as possible)
Jon T