I am a Reiki Master Teacher in Usui Reiki Ryoho (Traditional Japanese Reiki). I have been involved with Reiki for a little over 10yrs. I have been involved with alternative therapies in one form or another for twice that long, Japanese culture, philosophy, theology for even longer. I am Nationally Certified as a Massage Therapist and a Bodyworker (NCBTMB). During my time as a bodyworker, I have used Reiki on countless people with various results - the large majority of the time, positive in nature. I also use Reiki in combination with other therapies.
Today, Reiki in the West has been badly distorted. People talk about Chakras, crystals, auras, spirit guides, and a host of new-age parlance that has little to do with Reiki and nothing to do with Japan. Reiki has nothing to do with the chakras. This is because Reiki is Japanese. The Japanese use a version of Chinese traditional medicine (Tan tien and meridians) that was introduced to Japan between the 7-9th centuries. The Chakras come from India and were never introduced to Japan. An American man by the name of Arthur Robertson invented Tibetan Reiki in the 1980's and included the chakras into Reiki then. Usui, Hayashi - even Takata never taught the Chakras. If you know Japanese history and the History of Reiki, you'd know this bit of info.
Also, most peope today mistranslate the words Reiki. Most people are taught - and believe - that the word Reiki means Universal life force energy. It does not. If you translate it by using new Japanese script the translation could been seen as something similar to this, sure. The problem here is that Usui (the founder of Usui Reiki) died before WW2. WW2 was significant because it was here that the Japanese language was changed - changing the meaning of many words. When he used the words Reiki he was not describing a hand healing method. In fact, when Usui started to teach Reiki, hands healing was not even a part of the practice, hand healing was added several years later. It has been said by surviving members of Usui's school that when Usui spoke of hand healing, he used the words Teate or Chiryo-ho & not Reiki.
In old Japanese script, Reiki would be translated as spiritual (Rei) essence or awareness (Ki). 'Energy' is a very bad word to try and use for translation. This gives the impression of some kind of electrical energy. Ki itself is something that cannot be so easily translated - something few Westerners truly understand.
If you'd like to really learn more about Ki, I would recommend these 2 books:
"A Brief History of Qi" by Zhang Yu Haun & Ken Rose
"Ki in Daily Life" by Koichi Tohei
As far as Reiki goes, most skeptics are very correct when they say Reiki is Mumbo-Jumbo. This is because what they are talking about isnt Reiki at all - its about new-age Reiki or Neo-Reiki. Reiki in the West has been mixed, hacked, chopped, sliced, diced, blended, combined, simplified, and over exaggerated. It has been combined with everything from other therapies (such as theraputic touch TM) to new age spirituality, angels, and crystals. None of these things have anything to do with Reiki. I cannot stress enough to do your homework. Do not believe something just because someone says its so or because someone put it in print. Japanese Reiki is a tradition. A linage. Its not to be dismantled and combined with whatever someone fancies or believes. Its a sacred living Japanese art and should be respected as such.
In fact, Reiki does work, quite well I might add. It does not however use chakras, crystal, or angels to effect its results. If you would like to learn more about Reiki and how new age it has become, you may want to pick up the following books:
The Japanese Art of Reiki
The Reiki Sourcebook
.... both are written by Bronwen & Frans Stiene. They have done a large amount of research and verification. Wonderful education material.
I would also recommend staying far away from Diane Stiens book 'Essential Reiki' This book is as new age as it gets. She mixes Reiki with witchcraft, goddess worship, tibet, and the chakras - none of which is Reiki. IMHO, her information is grossly misleading, highly distorted, and just down right inaccurate.