I admit I've always been a big fan of auras. I
was never the sort of player who spent much time
counting card advantage (even when I play
control decks, which probably explains why I
never did well with control decks at FNM). Plus,
the feeling of building a monster out of
imperfect parts is just too much fun! So I'd
play with auras even if there were none as
powerful as Giant Spectacle, but it's a good
option to have around for decks that care about
enchantments and enchanted creatures. While it
doesn't have the massive growth potential of
Ethereal Armor or Armored Ascension, anything
that grants an evasive ability is worth looking
at, and once you're looking at red in general,
you can add dimensions that aren't always seen
in that sort of deck, from the obvious Lightning
Strike to the subtle Outpost Siege.
Auras are hard to evaluate, largely because they
depend largely on what you can attach them to.
At 2 mana, with the ability to immediately have
an impact, Giant Spectacle can prove to be a
Limited blowout by making a creature much harder
to block and still allowing you the mana to do
other things. It's usable on a small creature,
and it's also impactful on something large.
Auras are a bit fiddly to begin with, but I
think this one has a lot of potential in
Limited. It could maybe see Standard play in
small numbers if a deck wants some way to make
its creatures harder to block and has no other
way to do it.