Nearly all are cross breeds, yes. That does not mean that the labels are inaccurate - the species just don't correspond to lay-person's assumptions.

Trainwreck and it's daughter strain, Casey Jones, for example, have a heavily Indica dominant lineage, but behave veyr much like a Sativa. Casey Jones is amusing to bring out at parties: the volume of the room rises precipitously for about 20 minutes, and then... silence. :) It's very reliable.

The quality of the information on strains at the stores depends on the store you frequent. I tip well if the salesperson is knowledgeable and helpful.

I think we're in general agreement (and both a lot more experienced than the average person). I've seen things labelled at pure sativa which did nothing but cause people to feel couch lock, and pure indicas that lead to head highs in the stratosphere. I don't think the physiological effect is correlated strongly with the strain.