Well first off, they are a dedicated short bike, which will suit some riders and not others, but seing as your coming from a judge it will be rather similar to what you are riding now.
They ride very nice with the right set up and should last a little longer than most alu frames due to them being steel, and also will feel a little stiffer.
They have horizontal drop outs which you could class as either an advantage or a disadvantage. An advantage being that you wont need to run a mech or tensioner because you will just be able to move the wheel backwards and tension the chain. This can be a disadvantage as the further you move the wheel back, the longer the chainstays get and the less responsive on the backwheel the bike becomes. However, you can run the special chain tensioners with the hanger and just put a mech on.
Remember there are many other things that you will need to consider when getting a new frame. Such as revells have 4 bolt mounts, and as far as I'm aware, your judge doesn't so you will need to buy new mounts for around £10-£15 and also a new booster. As Ross said, you'll need a wide rim to fill up the gap between the rim and pads which will also boost up the cost, as you'll need a new rim, and a new wheel build.
So if you want something similar to your judge but slightly more trialsy and stronger, then yeah, get it but personaly I'd go for a complete change and get something longer, but thats just me.