USAIrways Signature Visa cardholders get many of the perks of Silver elite status:

• Unlimited space available upgrades
• Preferred check-in
• Preferred boarding
• Annual $99 companion tickets
• Complimentary US Airways ClubŪ pass (one-time visit)
• Discounted Club Membership (first year of a new membership)

Note that there aren't any bonus miles, so they're not fully bestowing Silver elite status.