Embarking on millennia-long journeys - What are the main obstacles to implement embryo space colonization missions?

From Wikipedia: Slow interstellar travel designs such as Project Longshot generally use near-future spacecraft propulsion technologies. As a result, voyages are extremely long, starting from about one hundred years and reaching to thousands of years. Crewed voyages might be one-way trips to set up colonies. The duration of such a journey would present a huge obstacle in itself. A generation ship is a type of interstellar ark in which the travelers live normally and the crew who arrive at the destination are descendants of those who started the journey. Human hibernation and cryonic preservation offer the possibility of sleeper ships in which the passengers lie inert for the long years of the voyage. A variant on this possibility is based on the development of substantial human life extension. If a ship crew had lifespans of some thousands of years, they could traverse interstellar distances without the need to replace the crew in generations. The psychological effects of such an extended period of travel would potentially still pose a problem.

http://en.wikipedia.org/wiki/Interstellar_travel

Embryo space colonization is a theoretical interstellar space colonization concept that involves sending a robotic mission to a habitable terrestrial planet transporting frozen early-stage human embryos or the technological or biological means to create human embryos. The proposal circumvents the most severe technological problems of other mainstream interstellar colonization concepts. In contrast to the sleeper ship proposal, it does not require the more technically challenging ‘freezing’ of fully developed humans. In addition, in contrast to both a sleeper ship and a generation ship the resources needed to build a spacecraft for an embryonic space colonization effort are considerably lower in terms of pure mass and complexity of the spacecraft. Furthermore, embryos may be launched from the Earth by cheap, yet human-incompatible, space guns.

http://en.wikipedia.org/wiki/Embryo_space_colonization

In the field of ectogenesis, an artificial uterus (or womb) is a mechanism that is used to grow an embryo outside of the body of a female organism that would normally internally carry the embryo to term. An artificial uterus, as a replacement organ, could also be used to assist women with damaged or diseased uteri to be able to conceive to term. Since the uterus is grown from the woman’s own endometrial cells, there would be minimal chance of organ rejection.

http://en.wikipedia.org/wiki/Artificial_uterus

What are the main obstacles? Here are a few examples: durable materials, cryotechnology, artificial wombs, androids capable of child rearing, landing on an extrasolar Earth-like planet. What is your opinion? Is fast interstellar travel the better option?