Long skinny workshops can be really good if you don't run big woodworking machines. If the benches are kept to one long wall and nothing more than shallow storage put on the other they can feel surprisingly roomy. Though as has been said you do need to be tidy otherwise you do end up working right by the door.
It's a shape well suited to a simple single pitch shed roof. There shouldn't be any need to triangulate the roof structure either so long as you tie a few rafters to both walls. Very easy to build and delivers huge amount of wall space on the high side. The only real downside of long workshops is that you tend to need more windows than other shapes if you want to avoid dark areas. Skylights might be worth thinking about either alone or in combination with windows.
Last I'd make sure you insulate it properly. The walls should be, in order, from the outside: external cladding, air gap, Tyvek, OSB/frame/insulation, vapour barrier, internal cladding. This keeps the workshop warm in winter, cool in summer and free of damp and condensation all year round.
A more minor consideration but I like plasterboard for inside cladding because it acts as a thermal store and if painted white reflects the light around nicely. I used two layers of sound rated plasterboard (like normal but a little denser) which doubles the thermal mass and means I can maker as much noise as I like without complaint from neighbours. Fair to say most others prefer OSB because you can screw stuff to it with greater abandon but I tend to feel they're missing a lot for relatively little.
