[iamaleksey]

> Cassandra is really awesome at writes but reads are really expensive

This is getting old, and is just plain untrue. Reads are more expensive than the extremely cheap writes, but they really aren't expensive.

> Atomicity at the row level only

Partition level, really, in modern terminology (apologies if that's what you meant).

[chaostheory]

> This is getting old, and is just plain untrue. Reads are more expensive than the extremely cheap writes, but they really aren't expensive.

It has improved a lot over time but it isn't a myth due to the fact that it's not good out of the box. You have to spend some time with configuration and mulling over the schema to mitigate it. It's something you don't have to really think about as much on other data stores.