Developer Mode still useful?

The Squarespace Developer Platform (including Developer Mode) was only available on version 7.0 - the previous version of Squarespace.

You can choose to build a new site on version 7.0, but you'll miss out on many of the Squarespace features that are available on the current version - version 7.1:

• Improved SEO
• Fluid Engine - the next generation website design tool.
• Better language support and integrated third party translation with Weglot. 
• Colours and consistency are much easier to manage with Colour Themes and section backgrounds
• Many new design features (too many to mention!) including text highlights, animations, section dividers, background art, new cart icons and more.
• You can design more quickly by copying content with saved sections
• You can add video backgrounds hosted on Squarespace (no need for YouTube or Vimeo)

If you plan to sell your work online, 7.1 also has:

• Store page support for up to 10,000 products (instead of 200 products on version 7.0)
• New Product Detail Page layouts