To be honest, I wouldn't bother taking the week off to play XIV at launch. I may end up sitting on my CE for a while instead of plunging right in on the 22nd, just because of how disrupted everything going to feel for a while. The only other alternative I see is to pick up another game to play during FFXIV downtime. Civ 5 is coming out soon (I think it's the day before XIV), so I might play XIV as much as I can and use Civ to soften the Downtime Blues.
As for "unplayable"... I'm not so sure about that. Your case seems to be rather problematic, but I assure you it is not the norm. Neither is needing 5+ minutes to equip all of Conjurer's starting actions, even with UI lag. And though I have as much a problem with UI lag as anyone else, I'm pretty satisfied with the core elements of the game. There are a handful of changes I'd like to see: AH (or at least Retainer searching), hardware mouse, auto and manual ordering of inventory, inventory filtering for equipping items, auto-templating of classes (so switching classes sets up your actions as they were), and obviously the UI lag. But Armoury is what drew me to FFXIV, and it hasn't been a letdown at all. I haven't tried partying yet, mainly because I haven't been able to play enough; but leveling Thaumaturge, Pugilist, Gladiator, Conjurer, and Alchemist have all been a lot of fun. I do a leve here or there, I do a little grinding, I do a little crafting. To me, it's a decent experience -- a lot of fun, but still needs improvement.