Contacts can be viewed in a list view by choosing, "Contact List" from the "View" toolbar button, or choosing "Contact List View" from the "Workspace" menu item. If you're in Contact list view and you're not seeing all your contacts (for instance the bottom of the window says 213 of 3503 contacts) then the most likely reason is that your current set does not have all contact categories showing, or is limiting what contacts you are seeing by tags. Another possibility is that you have something in either the filter bar in the top right, or you have a letter selected in the alpha bar at the top of the list.
All your keywords in Now Contact should have been imported as "Tags" in Now X. In Now X, keywords are "Tags". You can view which tags are being used to filter your list by opening the "Tags" pane by clicking on the second button from the left in the very bottom left-hand corner of your window. The first button there is your "Categories" pane, and the third button is the "Activity" pane.
To view categories and tags in the detail view of a contact, click on the same icons in the detail badge (the black reflective box in the top right corner of the detail window).
Categories work much as they did in Now Contact with two notable exceptions... a contact can belong to multiple categories, and because of this, a contact must have a "Primary" category that determines in what category style the contact will display.
For more information, you may want to check out the Now X tutorial movies (especially the "Introduction to the Now X interface" at: http://www.nowsoftware.com/nowxtutorials