I think game would be more interesting if players would have some movement acceleration. It means if you stand (with zero speed) and you push [W], you wouldn't get full speed at once but it takes some time to gain. It wouldn't have to be long time, only a few.
Next idea: What about dash? Imagine you have some energy bar which is still regenerating and you are able to use it for dash. Your speed will increase until your energy is at zero.
I think, if i look at the game now, it is static playing. This could help with it and make game more funny and action.