It is normal for it to leak a little gas all the time (this is one of the reasons there are growing health concerns about gas stoves). But it shouldn't be leaking enough that you can smell it unless you're standing right next to it. How far away are you picking up the smell? When the service people came out, did they look just at the stove itself, or did they also check the gas line connections to see if something else might have been damaged when the stove was installed? Might be worth asking your local utility if they will come check for a leak--ours will test the line to try to isolate where the gas is coming from.