Can all user's access the product and use it? For example, people with disabilities or special needs may be part of your target audience. Is the product accessible in some fashion for them as well. This one is being put first because it is so important and easy to forget that not every user experience's the product in the same way. It is important to remain cognizant of this fact.
You want to ensure your user can actually use the product or service. Is it functional and does it meet the user's needs? Also includes user testing, or a usability test, to get valuable feedback from the end user. This feedback will help the UX design process to check for any errors in the design. With this feedback you can make tweaks that will enhance the overall product. The topic of Usability is covered in more depth in a separate page of this website, found on the navigation bar.
Does navigation through the website, product, or service have consistency throughout the interaction. If there are hiccups along the way, you want to ensure that the user experience is seamless and not interrupted severely. Usability tests also can come in handy when checking for consistency throughout the product. Consistency also refers to the visual design of the product. Is the final result cohesive or jarring?
Hierarchy is how the content is chunked together to make the flow through the page or the interface more user-friendly. The important content is emphasized so that when the user scan's the document, website, interface, or object the most important information can be gleaned from a cursory look at the content. Walls of text and a scatter plot design where you can't find the essential information and objects are the opposite goal of good hierarchy.