It's a harsh fact of life and a quick look down the list of fixes in the older versions of SQL Server reveal some quite nasty bugs.

There is inherrent complexity in having fine grained multi-concurrent data systems. NoSQL is a very broad church so generalisations about NoSQL are risky. What I would say is that the NoSQL solutions are young and there will be bugs that we've forgotten we used to have in RDBMS's.

The companies behind the NoSQL products are energetic, enthusiastic and keen to improve their products. That is something to be welcomed.