The EULA for the beta patch says that "provided to end users specifically for evaluation and testing purposes only within the conditions of the licence agreement." What legal effect does that have for users who just want to play the game for fun?

If the game crashes, please report it. If you experience other major bugs or just want to suggest features, you should tell us. That's basically all it means. There's nothing implemented to enforce your legal obligation to do these things, so if you don't want to, you don't have to. The update is meant to bring enjoyment, so enjoy.

The EULA for the beta patch says that "provided to end users specifically for evaluation and testing purposes only within the conditions of the licence agreement." What legal effect does that have for users who just want to play the game for fun?
It means that you can't legally challenge T17 for anything that using the beta may cause to you or your computer. Also, if it doesn't work at all for you.

Having said that, those beta updates actually make the game more stable and secure than the latest official patch ever was.