Being a noob with barely a dozen games under my belt, my view is that High or WD are great. I've played Life and Light but never really 'got it' with them. High and WD on the other hand I think are good. I have admitedly lost more than I've won, but that has nothing to do with my own ineptness at all (!) so take my view with a pinch of salt, but have used WD to beat High Eleves, and High to draw with VC and Skaven (getting Fiery Con on a unit 40 clan rats and watching them reduce to single figures before getting into combat with my 20 saurus was enjoyable!) With Light I've lost to demons and Life lost to Bretts. I have lost with WD and High but feel that these best suit me and my style of play.
Yeah, I love High Magic. When we first got it, I was a little bummed. But as I've looked at it more and used it, I have come to thoroughly enjoy it. Especially Fiery Convocation. I see a lot of people saying they don't see its use after Turn 1, and that they swap it out immediately. Call me sick in the head, but I cast it over and over again if I get the chance. The high number of S4 hits (thank you, horde of Savage Orcs), plus the way my opponents use up their power dice to get rid of it, makes it a winner in my book. I also try to throw a Tempest on Turn 1 (S3 is just fine against Elves), and drop it for Shadow or Death. Miasma + Hand of Glory is killer. After High Magic, my favorites are Shadow, Light and Fire, in that order.
Coming from a long-time High Elf players perspective - it sure seems like the High Magic Loremaster is custom made to fit in the traditional Lizardmen build. Though I am attempting to take a combat-centered focus with my Lizardmen for tournament play (2 Oldbloods), High Magic would be my choice if I took a Slann. Having said that, I think the learning curve for proper use of the Lore (and it's attribute) is steep. I found when I was using the High Elf Loremaster (often along with a Lvl 4 Beast mage), my magic phases became extremely complex as the possibilities/tools seemed endless. Compound that with a mage who requires you to plan ahead for the spell(s) you are going to want/need 1-2 turns out and... Mind-blown. Much practice required for full benefit.