I'm the proud owner (and avid user) of a 5x31 IV bred Bold Sylveon and let me tell you from experience, it is well worth the effort and time it will take you (in regards to to the rarity of female Eevee) to get the proper nature on her.
Originally Posted by ImpendingChaos
Many folks may be runnin' her as a modest sweeper but they are simply missing out on her real strengths...an amazing dual screener and offensive-prone wall. With bold nature, max HP and some invested defense EVs she is just an utter tank. Top it off with Moonblast (singles) or Dazzling Gleam (doubles) for STAB damage and even without SpAtt investment she's just a pain in the *** for your opponents. I haven't opened a match without her since I got her bred. I primarily play doubles so it may be different if you're only a singles player too.
3DS Friend Code for Pokemon X : 4184 - 2414 - 9968