Newbie, I think there is also a big difference between fell racing and mountain marathons which you seem to be looking for. MM events require a different skill set to fell racing and I have no real experience of them. I have done the big sailing/running events but thats something else again. In fell racing, as has been said by others, GPS would be more a hinderance than a help unless you got lost and then you could get yourself back on track. IMHO, nothing comes close to nifty map and compass work as required plus a thorough run through the map with your minds eye before the event (unless you have reccied it).