Through September 30, 2013, the US American Express Membership Rewards program is offering a 40% bonus on points transfers to Virgin America Elevate. The usual transfer ratio is 200:100 (Membership Rewards:Elevate points), so through this promotion the transfer ratio will be 200:140.
Virgin America has a fixed value award chart for travel on their own flights, so their award pricing is based directly on the cost of a revenue ticket. So even with the transfer bonus you’re looking at a maximum of ~1.6 cents per point of value. That’s actually not half bad if you’d otherwise book a paid ticket on Virgin America.
But overall unless you have a specific redemption in mind I don’t find this transfer bonus to be especially compelling.