A vari-angle LCD is genuinely useful, especially when using Live View.

Main benefits:

• low-angle shots: compose near the ground without lying down
• high-angle shots: hold the camera above a crowd and still see framing
• tripod work: very helpful when the camera is pointed awkwardly, such as upward toward the sky
• discreet waist-level shooting: easier to frame without putting the camera to your eye
• self-portraits: possible if the screen flips far enough forward, though the display may be too small to judge fine composition from several feet away

Whether it matters depends on how you shoot. On many DSLRs, Live View is slower and uses more battery than the optical viewfinder, so some photographers only use the rear screen when they need the tilt/swivel feature. If you mostly shoot through the viewfinder at eye level, the benefit is limited. If you often shoot from unusual angles, on a tripod, or in crowds, it can be very practical rather than a gimmick.