Using "Reinforce Truth" on "Hero Kid" before activating this card can get you up to three more high-Level monsters for more high-Rank Xyz Summons, or additional copies of the monster you were going to Xyz Summon.
This card is great with "Gagaga Magician", allowing you to Xyz summon a Rank 7-8 with little effort.
While you have a face up Level 8 monster and at least two monsters you control are Normal Monsters, you can use this card to make them LV 8 to Xyz summon for "Thunder End Dragon".
Use with High level "Fortune Lady" monsters to give all other "Fortune Lady" monsters you control a game finishing attack boost.
Use in combination with "Tannhauser Gate", to make two of your monsters into level 7 or higher, then make the rest the same level, allowing for potentially multiple high Rank Xyz summons.
This card is superior to "Resonance Device" and "Star Light, Star Bright" in every way except for making it impossible to Xyz summon monsters of ranks lower than 7 or multiple Xyz monsters of different ranks.
This card works extremely well with "Superancient Deepsea King Coelacanth". Use Coelacanth's effect to special summon 4 Lv4 fish monsters. Next use this card to change all of their levels to 7. Next by overlaying the four fish, you can Xyz Summon two "Number 11: Big Eye". "Big Eye" can create huge card advantage for only the mere cost of two cards (this card and the discard from "Coelacanth"). Not to mention the 2 "Big Eye" are 5200 ATK + 2800 of "Coelcanth" = 8000 exactly.
If you plan to reduce a monster's level as opposed to raising it, it may be better to take advantage of a higher monster's level by special summoning "Level Eaters". That way this card will raise multiple monsters levels rather than decreasing the really high level of one monster.
If you already control a monster and still have your Normal Summon, you will have 5 monsters on the Field, all Level 8, so will be able to Xyz Summon both "Neo Galaxy-Eyes" and "Number 107: Galaxy-Eyes Tachyon Dragon" (or any other Rank 8).
In this case, Summon "Neo Galaxy-Eyes" first, since it will negate "Tachyon's" effect if it be Xyz Summoned after it.