Crygil announced on the official forums that the Nitro Boots ability has been shut down in arenas because the Blizzard team currently doesn't have "an acceptable solution" to the balancing issue. However, Crygil did say, "We fully plan to continue working on this item and we intend to adjust it in upcoming patches."

Further down in the thread, Crygil suggested players don't vendor the item just yet since the team has "plans to make certain that this item is still worth the investment made in it."