I’ve been using Google’s Inbox for the past couple months — almost exclusively, in fact — since getting my invitation, and my initial impression is that at this point it is pretty good for reading email but it currently has holes.
The most significant deficiency for me seems like a huge hole for anyone who does anything other than read and delete email: no access to contacts. None. No way to look for contacts or their information. No way to add addresses and information from email to contacts. No way to create contacts. (I have not tried using it with address lists.) It does use contacts to help address emails but as best I can tell, that’s the extent of its use of contacts. This, so far, is the one thing that has forced me several times to go back to Gmail when I needed to either look up something about a contact or create a new contact.
I like the ability to snooze emails (but I think Dropbox’s Mailbox does it better), and I like the ability to pin emails with “remember to…” annotations. Most of the normal Gmail keyboard interactions — aside from labeling, more on this below — for archiving, deleting, marking as spam, etc., work. I like that Inbox works well on my Android phone and tablet (both running different versions on Android, neither of which is Lollipop — something I can’t do with Mailbox).
The other significant hole is that Gmail’s keyboard interface for labeling emails (yes, I’m a labeler) is not supported. This would be a more significant gap for me at work, where I often apply multiple labels to an individual email and where I am almost exclusively on a computer (as opposed to phone or tablet), but even in my personal email I miss the easy/quick keyboard-driven way of tagging messages. Inbox’s current UI makes it difficult (maybe impossible) to apply multiple labels to a message, and is more based on the “messages in folders” metaphor.
I’m still hoping Inbox sees some significant evolution in the near future. Without that evolution, I’m likely to abandon it and go back to Gmail. I would be giving up the annotated pinning and message snoozing, but would still have better-than-just-decent interfaces on phone and tablet, integration with contacts, and full keyboard interaction support when at a computer.