Everyone gets usability, right? UEs design and test, and design some more until customers can use the product (it's usually a product, since we don't usability test services much, yet) easily. Utility, we mostly get that. The product is supposed to meet a customer's need. In the worst case, ensuring utility means walking down a list of features the product is supposed to contain. If we're really conscientious, we create a contextual task analysis and design a "whole product" solution, in which the product either supplies a complete solution to a need, or the product complements are easily available to the customer.
Identifiability is the product's distinctiveness, its uniqueness, the design edge that sets it apart from its competition. Think iPod. Product marketers get this, I think, but there are an awful lot of "me too" product and e-commerce web sites out there. We recognize identifiability when we see it, but practice it too infrequently.
Trustability isn't obvious at all, but when I talk to user experience designers about it, something just clicks. Lots of people have had the experience of finding something for sale on a e-commerce site but were unwilling to purchase from the site. Why? The site was easy to use, it was distinctive, it offered the product we wanted and good delivery terms, but we just couldn't click the "purchase" button. We went elsewhere. This is a classic trustability issue. We didn't trust the site, or the company, or something else, and someone lost a sale.
I've done a fair amount of research on trustability. It's a great topic. As a VUI designer I've found that the quality of the system's voice has an aspect of trustability.
All of the "itties" that I mentioned are important, but my observation has been that people involved in product development tend to focus their efforts on one or two. Designing and measuring the full customer experience requires that product designers address all of the itties.