From my point of view, I don't like using mint custom search because:
It doesn't preserve google search options and layout (left menu with video/images/Any time/Hour ago...), so when you are used to standard google from other OSes, you stare at mess mint search makes. Maybe its design that takes too much of top space (around 1/3 on my screen), is too colourful and aligned to left with no padding.
I miss integration with google account/plus/picassa (I mean grey bar on top of google pages , not links going through 3 external (redirecting) sites). Btw what is that redirection ( google/cse -> search.linuxmint.com -> some google site ) good for?
And one question, is it true that most of your income comes from custom google search? I don't get how because I don't see any ads or anything.
I write this as I see mint search one of most annoying parts in mint. While I think it got better from what it was first time (its faster imho) there is still space for improvment and that small changes could solve annoyance it generates.
PS: I dont like that only way (I found) to add standard google to search box is to delete your custom one and then add standard.