Hello,

I would say that it comes down to what you care about in your key. If you can build a compound key that will provide you an appropriate level of uniqueness, but is meaningful to your developers, that may be a way to go. If you can't, or you don't care about it being meaningful, letting the system generate is unique key on your behalf means you don't need to worry about how the key is constructed and what may happen in the future to the properties you would otherwise have used in a traditional compound key.

Thanks,
Mike

pyGuid is useful in scenarios where you cannot define a clear cut key. 

For example, we have to multiple case notes against associated to a case. 

pyGUID is used when the property that could be used as the key is not unique.

The cons of using pyGUID is its make use Obj-Open or Open by Keys tough as the key is auto generated

pyGUID is also good if you need to create some record before you fill out other data on the page. Once I used this approach because the property which could be potentially used as a key  wasn’t available in the begginning but I was forced to create some references to this object during create process. 

pyGUID is also good if you don’t care about value of the key. 

I think, in general we could apply the rules and best practices from relational DBs