Do not download the 1.2 update
The 1.2 update for Crimson Dragon Side Story allows it to function on WP8 and apparently has some other miscellaneous fixes. So why shouldn't you download it?
They closed the loophole.
As you may know, every completion of World 5 on versions 1.0 or 1.1 of the game would grant you the "first time bonus" of 15 jewels upon completion of World 5, the final boss.
This tied in quite nicely with the awful awful Dragon Master achievement for killing Dark Phantom 200 times and the White Reaver Unleashed one for awakening all skills.
Thanks to Zebrasqual we know that to unlock all skills you will need 3294 jewels. Well, 200 runs of World 5 at 15 jewels a time is 3000 jewels.
Obviously you'll have killed Dark Phantom in Mission Mode a number of times so your actual jewel number upon the 200th kill will vary, but when you unlock Dragon Master you can assume you'll have around 3K from gameplay alone, not counting GPS and Leaderboard jewels.
Thanks to the 1.2 update you will pretty much have to spend Microsoft Points should you ever hope to obtain all the achievements when the leaderboard and GPS gives you such a pitiful amount of jewels.
Considering 1000 jewels is 800 Microsoft Points, that's a huge pay wall to place skills and the related achievements behind. What a disgusting and underhanded practice.
tl;dr version: Don't update or you'll face the costliest 200G ever.