First of all, let me start by saying I've used practically every diagraming, chart-making, and wire-framing tool on the market--from desktop applications like Omnigraffle and Microsoft Visio to web-based alternatives like Gliffy and Draw.io. Of any of the tools I've used, Lucidchart is the most versatile, the most robust, and certainly the most user-friendly.
Because Lucidchart is web-based, it works equally well on Mac's, Windows machines, and Linux boxes. Gone are the days of having 3 separate tools for 3 different operating systems. Unlike Lucidchart's competitors, Lucidchart is capable of importing AND exporting Microsoft Visio files. It is also able to import Gliffy and Omnigraffle files, as well as Visio stencil files.
Lucidchart's robust shape library makes it a good fit for just about any project. If you can't find a built-in shape library for whatever you're doing, Lucidchart can import both SVG files and Visio Stencil files. In addition, it supports fully-interactive documents with embeddable videos, clickable areas, and the ability to embed your document on your own site, in Atlassian's Confluence/JIRA applications, and in your Google Drive documents.
TL;DR: Lucidchart is fantastic, and I highly recommend it.