Handiness often implies that something is easily carried or saved for when needed. The handiness of a smartphone allows us to access information anytime.
Pro Tip 2/3
Context Specific
The object's handiness is better understood when its specific usefulness is mentioned. Gardeners really appreciate the handiness of a multifunctional trowel.
Pro Tip 3/3
Positive Connotation
Handiness often conveys a positive judgment, expressing satisfaction with how well something works. I was struck by the handiness of the new kitchen gadget.