The Scottish Government, acting through the Scottish Parliament, has always had the power to vary (up or down) the level of income tax by up to 3 pence in the £. It has never used this power. The latest proposition is that it should have even greater power to vary the level of income tax. But will any political party actually want to?
Control over stamp duty, landfill tax and air passenger duty is not be sneezed at - but it is hardly a significant change in the parliamentary terms of trade.
Similarly, responsibility for airguns and for the administration of Scottish parliamentary elections is not wholly negligible, but in the wide range of powers already available it is fairly marginal.
So, nothing to get too excited about.