The lag was and is Terrible to quest/grind in! As well is the constant "World Server down". But despite all that, I just kept going anyway. Takes allot of Patience to endure that! At times it was a test of will it seems like. Yeah, its only Beta but leveling still takes Allot of Effort and perseverance to do so with massive amount of lag and server downs as well as testing things out along the way.
At 80 you do get a Achievement flash across the screen for hitting lvl 80 as a accomplishment. I missed it since I was taking a clean UI screenshot. Achievements also appear to be zone wide also whenever they happen.
This was how I progressed: Howling Fjord with (Nexus Coldarra area in Borean Tundra) > Dragonblight > Zul' Dark > Sholazar Basin > Icecrown. I didn't do any quests in Grizzly Hill or one of the last zone of The Storm Peaks. Barely did any in Borean Tundra other than the Nexus area quests.
I leveled entirely as Protection spec as always and in Full Tank gear. I made a big effort to wear WotLK Armor gear as I leveled as well to test it out leveling the entire way from 70-80. Just about everything is documented in my blog.
With my tBC gear i used from 70-74 with some WotLK blues from quests or Instant quests. From 74-80 replaced some my gear/weapon with crafted Saronite gear as well as crafted Daunting Tanking gear you can get crafted at 78. Numerous Trinkets you will pick up along the way as well. I find the crafted Blue Saronite & Daunting gear to be rather good Plate gear with lots of Stamina/Strength/Defense Rating.
Outside of Instances most the Plate gear that drops seem to drop in lvl 74+ zones of Zul'Dark, Shalozar Basin, Icecrown.
Other Observation since last Patch.
Change to Shield of Righteousness damage nerf is quite noticable on 1-3 targets. Especially on one target where it now takes a noticable longer time to kill a single target.
Also noticed had more HP as well. I though I was mistaken noticing did seem HP was increased somehow.
Hammer of the Righteous, not sure if its in the notes somewhere on the maintankadin forum as havent had time to read all those threads. But with the latest change to HotR as it says in the tooltip it seems to hit roughly for 3.03 x the DPS on your character sheet DPS. HotR damage is also affected by your AP which affects the DPS on your character sheet. Hits with HotR does increase with higher AP.
*For the next expansion of WotLK it will of course be much easier for you to get from 70-80 with a polished game working Server and much less lag of course.