I do not own nor have ever tried a high end plane, and therefore I am biased against something I have never experienced.
I currently own a Groz #4 plane. It sells for about $38. Not dirt cheap, but not expensive at all for a new tool. What's the difference between this and a high end tool? Not-so good finish, sole/back of blade not being too flat, inferior castings, and more backlash in the adjustment system. All those problems can be fixed with work(except for the finish + casting).
The performance of a tool relies heavily, but not solely, on the skill of the user, in sharpening and in use. Now I'm definitely not an expert on hand planing, but my results improved much more after practice(including sharpening) than after fettling.
Now you might think: should I buy the really nice plane? Yes, just keep in mind there are alternatives. Nice tools help out in, but don't automatically make, good work. Also for those who are thinking of buying more hand tools so they can incorporate them more into their work, go ahead, it's hard to do this with a $1000 tablesaw.
My final words; this plane works for me and it will probably work for you.
Now on a less serious note, I was part-swapping between my miller falls jack plane and my Groz #4, and I discovered that the jack's frog fits my #4, also the adjustment screw is interchangeable, they have the same thread.