There's nothing special about the two words that requires capitalization. In general usage it would look like this:
We can pour user experience awesomesauce on your product because we outsource to Ukranian user experience designers and mark up their work 1000%!
In the latter instance, you may choose to formalize the title with capitalization:
Hire our Ukranian User Experience Designers and get a free iPod.
When you're speaking to an insider audience, UX or UXD has become shorthand for user experience design. Sometimes it actually represents interaction design (IxD) or (worse) graphic design. But only the purists among us seem to be concerned with such semantics.
Skillz: SEO, Flash, Banner Ads, UX, Branding
Or you can [accurately] distinguish the design aspect (vs research):
Mo skillz: UX Mumbo Jumbo, UX Research, UX Design
Industry buzz words and insider speak (like acronyms) almost always earn bonus points with recruiters. Since you'd typically be trying to show up in a search, it's best to cover your bases with a little redundancy.
You should hire me because I do User Experience Design (UXD), Interaction Design (IxD), Information Architecture (IA), and Pseudo Design (PxD).
Consider your résumé powered up!
In spite of the fuzzy rules of the English language, do not hyphenate the terms under any circumstances. Unless you're applying for an English professor position. Then you want to check with another SE site.