I want to know, from experienced software vendors...
How much effective to have separate commercial and (discounted) personal/non-commercial versions of a product (with same features)?
In that sense, if much "commercial" users cheat by buying the non-commercial (or "educational" or other alike discounted) version, still makes sense to have these separation?
It can often make sense to have both a paid commercial version as well as a free or low cost personal version. Of course it depends on the product, but if you look at virtually all large software vendors you will see that they offer multiple versions on at least some of their products. If it didn't help them make more money, they wouldn't do it.
It is important that your commercial version have features and capabilities that are important to corporations that are not available in the personal version. That way commercial clients would need to buy the commercial version to get the features they need and can't cheat by buying the personal version.
As an example, consider a database application. You could have a personal version that was limited to 10,000 records with no audit trail. For the commercial version you could support an unlimited number of records and full SOX compliant audit logging. The personal version could sell for $10 and the commercial version sell for $10,000.
Of course if your application is a game like angry birds, then there is probably no reason for a commercial version; what feature could you add to make it compelling to corporations?