[freels]

This advice is highly implementation specific and unnecessarily dangerous. For read only transactions, a well designed system will be able to provide SNAPSHOT isolation with little negligible perf impact compared to READ UNCOMMITTED. When combined with SERIALIZABLE write transactions, reads at SNAPSHOT are equivalent to SERIALIZABLE.

For transactions which must write, the entire point of this article is that anything less than SERIALIZABLE leaves you subject to anomalies whose affects on your data can be very difficult to predict beyond trivial scenarios.

If you must lower consistency for performance's sake, then so be it, but I would strongly argue that should be the exception, not the rule, and not be a decision made lightly.