I do use these - every little percentage helps. I particularly use them where i am still below the diminishing returns values for slotting on a particular power, where I can boost it just enough to not have to add another slot to the power.
For example, to boost 2 recharge rate IOs +5 each in Hasten to allow me to get to a perma Rage without having to add a third slot on Hasten. It was a small span that I was able to bridge with the boosts.
After talking with several people in-game, it has occurred to me that more people do not take advantage of the enhancement boosters than I originally thought. Do you and what are your reasons/results? If you do, how far have you boosted?