Old School enthusiasts would say Martha has 3 things going for her:
1. Solid Runway--Dior, Dolce & Gabbana, Gucci, Victoria's Secret
2. Solid Editorial--NUMÉRO China Feb. 2011, Vogue Covers, etc.
3. Solid Campaigns/Advertising--luxury clients like Bergdorf's and Neiman Marcus, and H&M
As a New School enthusiast I'd add Martha also has 4. Solid Press Potential--via internet, largely because of her effortless sense of fashion and personableness with photographers. Above, she maintains her classic style base, yet still accessorizes with trendy round sunglasses and platform shoes.

p.s. I've been tweeting with regularity now, in case you want to follow @altamiranyc