Let's talk about "subliminal communication," what some in marketing like to term "hypnotic communication."
Whenever I read a page and it starts to say "Imagine..." my antennae start vibrating. There is someone very amateurishly trying to use hypnotic communication. They are trying place you into a certain state of mind, but going about it the wrong way.
Ideally the subject should be affected without their knowledge (hence the "subliminal," which means "below consciousness"), seemingly without any real effort on their own. Yet, when you say "imagine" you are a) placing your intent right up front, and 
requiring action, focus, and concentration from your subject.
A classic example might be, "Imagine you're walking down a white sand beach, as gentle blue waves lap up toward you." You're asking them to do what should be your work. Dump the "imagine." Paint the picture, use the words, and their mind will naturally pick it up. "You're walking down a white sand beach, as gentle blue waves lap up toward you," is infinitely better. Throw in the "imagine" and you're building resistance and making your job 100% (at least) harder.
That one word -- "Imagine!" -- throws the whole machine into reverse.
It gets even worse when someone with absolutely no training or study time starts trying to write "hypnotic" marketing messages. "Imagine all your problems are solved, you're living in the lap of luxury, driving the car of your dreams..." *BLECH* You've seen the web pages and magazine ads. The problem here is compounded in that a vivid picture is not being painted. There's nothing there to imagine. What does "living in the lap of luxury" mean? What does "driving the car of your dreams" look like? Sound like? Feel like? What emotions does it bring up in you? That's the stuff the hypnotic message should be composed of.
Presenting these images, describing these sounds and feelings, calls them up in the reader/listener in the same way a good novel places them smack dab in the author's conjured world -- that's what you're after. "Imagine" is the clunkiest, most counterproductive way you could ever use to try getting there.
Still, I see "experts" and "professionals" using it. I've even seen books saying that's the way to do it. I can only shake my head and question how "expert" they really are. It might be a nice way to get the neophyte's mind moving in the right direction, but using the word "imagine" in actual practice is like trying to win an Olympic Gold Medal in swimming while wearing water wings, a life vest, and a snorkel. It should never be done.