I leveled straight holy/shockadin. This was my spec when I dinged 70:
http://www.wowhead.com/?talent=sVxuzgzGestZVf0x
My goal was to get up the tree as fast as possible, i.e., Holy Shock at lvl 50, and so only put 5 points into each talent tier, and then went back to fill in the gaps afterward.
5/5 in Divine Intellect
5/5 in Spiritual Focus
3/3 in Healing Focus, 1/1 in Aura Mastery, 1/2 in Unyielding Faith
5/5 in Illumination
1/1 in Divine Favor, 3/3 Sanctified Light, 1/2 in Improved Blessing of Wisdom
5/5 in Holy Power
1/1 in Holy Shock, 3/3 Light's Grace, 2/2 in Improved Blessing of Wisdom
5/5 in Holy Guidance
1/1 in Divine Illumination
Then tossed 10 points into the Ret tree, then 2/2 into Purifying Power, 3/3 in Blessed Life, and then finished out 5/5 in Conviction.
I could do decent/acceptable damage with this build and felt quite survivable while doing it. I could solo most mobs a level or two above me on a near continuous basis (with about 20 seconds per kill) and rarely stop to drink. I could tank appropriate-level instances up through Sunken Temple, much like ret pallies can heal anything in Azeroth effectively. In my experience, the Shockadin build is nothing more than an alternative to levelling ret. I can't in good conscience recommend that anyone level like I did, but if you try doing so, you can successfully do it without being perma-gimped.
As the FAQ says clearly though, "Shockadin is something Holy pallies do to solo/grind when they're not raiders." When I decided at 70 that I was going to heal 5-man instances with an eye to gearing up for Kara eventually, I switched to something quite close to the FAQ's cookie cutter raid build and immediately saw my solo DPS plummet dramatically. Try to get the Nagrand Nesingwary quests, for example, completed as Ret, Prot, or even with a ******* of a Shockadin build like this one, before switching to a raid healer 41/20/0 build.
I don't think I leveled all that much slower than some peers who started at the same time and played about as much as I did. A true ret levelling build likely would have been much more effective overall.