Adema--I don't walk a single step off snow without Cat Tracks. Nothing wears your boots out faster than walking around in them. And the wear they suffer devastates performance, and even safety, because the interface between boot sole and binding is critical. I typically wear out a couple sets of Cat Tracks a season!
They are a pain in the neck to get used to, and they need to break in before they are at all easy to use. But it's a habit that is well worth developing if you value your boots and your skiing! Many instructors I know have modified theirs by attaching little cords to the tabs in back, to make them easier to get on and off. But I find that, once you've used them a while and stretched them out some, they are actually very easy to use. Hint: don't grab the tabs at all--grab the entire back section!
They do NOT really make walking easier, as their advertisements promote. Indeed, you have to learn to walk carefully so as not to pull them off. Their sole (pun intended) value is in protecting your boot soles, and they do a good job at that.
You can buy Cat Tracks at pretty much any ski shop these days, for $12-$13 dollars or so.