About EM Gauge.
This being an entirely light-hearted view on the subject! 
The Class 20 on the left is on Peco OO finescale track- the 25 on the right is on SMP EM gauge track- the exact difference in gauge is 1.7mm
my need to go to EM gauge was based on the fact that I had modelled US outine for a number of years, and got used to the HO scale models - the UK ones no longer looked right on the same track! - I'd always been put off by the fact that you (generally) have to construct your own points in the finer gauges.
Deadwater Burn- having only one point- was an ideal testing ground for trying out EM- have to say I am totally hooked and building pointwork is far more rewarding and theraputic than you could imagine- see the track construction page:http://www.freewebs.com/deadwaterburn/gallerytrackconstruction.htm
Rolling Stock conversion is reasonably straight-forward, especially with diesel locomotives. Steam loco's or shunters with coupled wheels present more problems. For more info see: http://www.emgs.org/