Is using testNg priority good?

Using priority to drive order of execution is perfectly fine, but the question is why do you want to execute test cases in a certain order? As a general rule test cases should be atomic and should not be dependent on other test cases. In such cases do you worry about the order of execution? I rather don't pay much attention to order of execution unless it's an explicit requirement. e.g. If my login test case fails then I don't want to execute the rest of the test cases in suite as those will likely fail. In such a situation, I would use hard dependency to drive.

@Test 
public void serverStartedOk() {} 
@Test(dependsOnMethods = { "serverStartedOk" }) 
public void method1() {} 
You can also have methods that depend on entire groups:
@Test(groups = { "init" }) 
public void serverStartedOk() {} 
@Test(groups = { "init" }) 
public void init Environment() {} 
@Test(dependsOnGroups = { "init.*" }) 
public void method1() {} 
You can also use soft dependency to drive execution order. By "alwaysRun=true" in your @Test annotation.
Know more at the TestNG site