Plastic models are the way forward and GW is bringing out more and more plastics. This way they can keep the costs of producing lower then with metal and finecast models and for us it makes it easier to convert models. The amount of detail is outstanding with plastics but it has one drawback, plastic models are very lightweight. They have the tendency of bouncing to the other end of the room when you drop them.
But there's an easy solution for that. I stick a 5cents euro coin in the bases to weigh them down a bit and it works really well. Models don't get knocked over on the table and stay in their place nice and sturdy. I imagine that every currency has a coin with the size of a base so if you're not in the euro zone you might have to have a look which coin fits or go to your local DIY store and pick up some washers. This way you also add a little value to the models. A unit of 10 models costs me €0,50 so that's not much .
But why stop there? I also magnetise all my bases. I started doing this with my fantasy army as they have to be placed on movement trays. so when you magnetise the bases and get a metal sheet and cut that to the size of your unit they will never fall of and you can easily move them around on the table.
But why do this with 40K models then,.. well you can put your models on any metal tray for easy transport. the models will stick to the tray even if you turn the tray upside down. I have seen DIY cases that fit metal serving trays and have magnetised units on them.Also you can imagine that when you attend a tournament and have to move between tables a lot that it's very easy if you have one or two of these trays and you don't have to worry about people bumping into you when you make your way through the crowded room with your precious painted models.