I apologize in advance for my ignorance of how things work around here, as I'm new and I've just signed up.
I was on my 1.8 multiplayer server attempting to create a pair of leather boots that give me ("the wearer") a speed boost of 25% while they're equipped, among other NBT tag-related tomfoolery. However, I have been unable to get them ("the boots") to affect my ("the wearer") speed (nor FOV, for that matter) at all, regardless of whether the item is in my hand, equipped, or both. The command I used is as follows:
/give Sunruine minecraft:leather_boots 1 301 {ench:[{id:2,lvl:4},{id:8,lvl:3}],display:{Name:"ORBIT Runners",color:16384000,Lore:["Light and fast."]},AttributeModifiers:[{AttributeName:"generic.movementSpeed",Name:"generic.movementSpeed",Amount:"25",Operation:1,UUIDMost:44938,UUIDLeast:103883}],Unbreakable:1,HideFlags:7}
My environment is Windows 8.1 Pro, latest version of Java at the time of this post, vanilla 1.8. I hope this is of any help, best of luck to you.
Also, and I'm not sure whether or not if this is related to this particular bug or not, the boots display as the <a href="http://hydra-media.cursecdn.com/minecraft.gamepedia.com/f/f4/Lockedchest13w18b.png?version=00842beccb7f5b7368790e0c653f8d29">purple-and-black checkered block</a> in my inventory rather than as red leather boots like they're supposed to. I have not tested whether this is exclusive to this issue, however.
I just attempted the same /give command that I used in my above comment using a 1.8.1pre-3 client on the same 1.8 server and received the same result.