What about the orexin (hypocretin) receptors antagonists for the treatment of insomnia?

In addition to the psychological approaches, primary insomnia is treated mostly with benzodiazepines and other hypnotic drugs such as zolpidem, zopiclone, and zaleplon. However, new compounds called the orexin antagonists, such as suvorexant (Merck) and SB-649868 (GSK), are currently under development. The preliminary results are fascinating: Major sleep efficiency and total sleep time improvements; No SWS nor REM sleep reduction; No tolerance nor any rebound after withdrawal; Efficacy from the very first night to the end of a 4 week treatment; Improvement on both objective PSG measurements as well as on patient subjective questionnaires. No major side effect, except for daytime sleepiness in 2% of the studied samples. For me, it sounds just like they have found the ideal treatment for insomnia. Have you heard about these substances? What do you think? Are you aware of any fundamental or clinical research conducted with those compounds?