#209 - March 31, 2009, midnight
To try and clear up any confusion, the planned item level for the achievement in Ulduar 10 is item level 226. This level gear drops from both hard mode Ulduar 10 and regular boss kills in Ulduar 25. So yes, while players who clear Ulduar 25 will get more 226 gear at a faster pace and possibly get this achievement first, it's an achievement anybody can do, so when a guild that only runs normal Ulduar 10 progresses through the instance and gets the hard modes done, they will be ready to take on this achievement.
Reward: Herald of the Titans (title)
If you primarily run 25 player instances and want to get this achievement/title, just hang on to your Kel'thuzad weapons and regular Ulduar 25 boss kills and you should be good to go.