Short report: Buy them.
Having just come back from a 100k ride (first time I've done that in close to 15 years I suspect) it makes a significant difference. You can use them just like you had a front gear, ability to go from eco to sport and back down to eco without having to cycle through turbo is great. makes for a much smoother transition as well, and no more taking hand off the handlebar when wanting a power boost whilst heading up a hill.
Just as easy to use as if they are covered or uncovered. Uncovered is slightly easier to find but doesn't take long to remember where they are. Buttons worked well where I had them, I spend just about all my time on the hoods.
I have no idea of what these cost in US, but NZ$110 (including a 15% sales tax) equivalent in US is US$73. Based on other things I imagine they are cheaper in the US, but even at that price no hesitation in recommending.
For what they probably cost to make (they are not complicated) Specialised should consider giving all those with last year's CREO free buttons if we go into the LBS and get them installed. Makes for a much better and much safer experience.