Redis does not use the Relational Model not because it promotes a simple key-value model, but because it proposes a different paradigm and data model based on fundamental data structures.
MongoDB for instance does not took away the relational model at all, in some way. So what NoSQL are we talking about? :)
NoSQL was a good marketing idea at start, but now it's starting to be really misleading.
I don't care about "NoSQL" - I like Postgres and SQLite. What makes the individual "NoSQL" databases interesting, though?
Redis is in a design sweet spot, IMHO. The pure key-value stores seem way too low-level to me, but the support for atomic operations on lists, sets, etc. in Redis is very handy. It also works well as a cache for other databases, and newer commands like BLPOP are very cool.
While I haven't used CouchDB much, its model is also interesting, and I can see its trade-offs being an excellent fit for certain problems (just not mine).
"NoSQL" is about as useful as rallying behind "languages without camel-case" (NoCC!).