[daxterspeed]

Personally it's the bundles and pinning. The bundles just worked more consistently than Gmail's tabs and made it feels fast (and safe!) to quickly archive a bunch of promo emails you weren't currently interested in.

Stars can be made to work like pinned e-mails, sort of, but it not consistent across the mobile app and the website and the UX just feels unresponsive in comparison. Pinned emails were much better separated than starred emails are today.

I think a bonus aspect was just design. Inbox didn't have to support as much legacy as Gmail and its design ended up being really sleek. Inbox overall just felt faster than using Gmail.

[piccolbo]

Bundles are like thematic inboxes. So I can go into work mode, family mode, news mode and stay there for a while but look only at things that have not been taken care of yet. If you try and replicate that with a filter, inbox actively prevents it (label: something AND in:inbox). It won't show anything. Even apple mail allows that. Also the de-emphasis of read/unread status. You can archive without reading more than the subject, and it doesn't show in all the unread counts etc. When unread counts are so much in your face, it's hard to ignore them.