ToodleDo is available wherever I need it (website, app, mobile, input by email). The UX is intuitive, elegant, and fully featured without bloat. It's perfect for implementing GTD and flexible enough to sort, tag, filter, visualize any way you'd like. Task creation is intuitive and natural (e.g. "/due next Friday" adds the appropriate due date for next Friday). And finally, it's visually appealing enough to make me enjoy using it. I've been a user for years at various increasing paid tiers and have found each one well worth it. Review collected by and hosted on G2.com.
The "hotlist" automated sort is a little opaque (though sometimes helpful), but it's easy enough to create your own custom views. Review collected by and hosted on G2.com.
