<p>It depends on what program you are enrolled in. For life sciences programs (mol. bio, biochem, genetics, cell bio, etc.) students can expect full tuition and fees remission, health insurance, and a generous stipend if attending a 1st-2nd tier institution. This is because of funding received from the National Institutes of Health, which has a large budget (and hopefully larger with President Obama now in office).</p>
<p>For programs with less federal support (say, english or flim studies), one would almost certainly have to TA and expect a lessened stipend/salary.</p>
<p>I think getting some TA experience is a good thing, but overall, the best funding level to focus strictly on research/dissertation would be your #5.</p>