Thank you Big Uncle, TK and everyone for sharing so much information about this great dakini-Buddha.
I've read about this Buddha and although the most popular proponent of this tantra in recent times is HH Pabongkha Rinpoche, the benefits and greatness of this Tantra has been proclaimed much earlier by the Sakyas. I'd like to share with you what I read:
The second important practice (note: first being Hevajra) is a practice cycle whose main home is the famed Sakya collection of the Thirteen Golden Dharmas. This is the very popular cycle of Naropa’s Khechari, or Naro Khachod as she is known in Tibet. If Hevajra is the pillar of the Sakya lineage, Vajrayogini is its heart.
*Lopon Sonam Tsemo told his brother, Jetsun Rinpoche, “Of all the instructions I possess, Vajrayogini is the most profound.” Thus, the unique Vajrayogini teachings of Naropa were preserved only in the Sakya school for hundreds of years and did not truly began to spread to other schools until the fifth Dalai Lama received them from Nesar Je.
The Vajrayogini teachings are Naropa’s unique transmission. He received them in a vision of Vakrayogini and passed them solely to his two main Nepalese disciples, the Phamting brothers, who made their home just below the Asura cave in Pharphing near Kathmandu, Nepal. After one generation, these teachings, along with the Chakrasamvara-tantra, arrived in Tibet with Mal Lotsawa, a guru of Khon Konchog Gyalpo and Sachen Kunga Nyingpo. The Vajrayogini teachings center around a short sadhana and a set of profound completion-stage instructions, especially the instructions of “the meditation beyond thought.”
In general, the teachings have a common and an uncommon form, which differ primarily in details of the guru yoga and completion-stage practices. It has been said that more masters have realized Buddhahood in the Sakya lineage through the practice of Vajrayogini than through any other practice. Compared with the Hevajra system, Vajrayogini is extremely easy to practice and understand; for this reason, the Sakya tradition of Vajrayogini has become very popular all over Tibet, regardless of tradition.
From: Pg 252 & 253 of Treasures of the Sakya Lineage: Teachings from the Masters (Paths of Liberation Series) by Migmar Tseten with foreward from H.H. Sakya Trizin
*Lopön Sönam Tsemo (1142-1182) and Jetsün Drakpa Gyaltsen (1147-1216) were among the "Five Exalted Masters of Sakya" and were both instrumental in systematizing the various teachings of the Path and its Fruition cycle.