Please tell us more about this.

Places with more STRs will provide a more accurate report based on numbers.One with fewer STRs will force the algorithm to pull data from outside your exact filters.

Are they more/less desirable than a typical owner-occupied note?

You have to learn what you are willing to accept as not perfect, but good enough. 

I would NOT advise a client to ever purchase a tenant occupied property with uncooperative tenants unless they are very experienced investors or the property purchase price comes at a discount that reflects this fairly major issue they are conveying to you with the sale.How long has this place been on the market?

This can be a huge range.

The good contractors won't have an issue with this setup.

The 50% rule - in my opinion- is used solely as a quick back of napkin calculation to determine if it is worthwhile to do more investigating of a property. 

@Jorge Newbery Can you comment on this?

If you want to verify the mailing address and send your sellers a mail piece, this data source works great.