1. Managing shards and the mongos router layer should not be dubious, IMHO. Additionally - there should not be a SPOF if you've designed the architecture to leverage the native scalability aspects of MongoDB. That said, if you struggle with management, you can certainly leverage an online service that greatly simplifies not only scalability but security, manageability, and availability as well.
2. I don't know the read/write profile of your app but based on the hundreds of apps I've helped to configure and size, I'd be inclined to suggest that you don't need a Redis cache if you're configured properly.
3. Interested in that roadmap... haven't seen it... what specifically interested you?
4. MongoDB has similar available... happy to share that with you.
You're certainly free to choose whatever solution you believe works best for your use case. However, the points you've made don't appear to provide compelling arguments for Couchbase over MongoDB.
Precisely, you made my point when you acknowledged that MongoDB allows me to get a critical thing so wrong. And if I get it wrong, the pain afterwards is so intense when you go back to fixing it. Thanks.
I forgot to mention, Couchbase also guards me against the rogue DBA situation by ensuring field level encryption under application control. A huge plus.
2. I don't know the read/write profile of your app but based on the hundreds of apps I've helped to configure and size, I'd be inclined to suggest that you don't need a Redis cache if you're configured properly.
3. Interested in that roadmap... haven't seen it... what specifically interested you?
4. MongoDB has similar available... happy to share that with you.
You're certainly free to choose whatever solution you believe works best for your use case. However, the points you've made don't appear to provide compelling arguments for Couchbase over MongoDB.