I’ve never had a problem using a container DIV and the margin: 0 auto; way. Maybe instead of div#pagewrap, use JUST #pagewrap for your CSS descriptor. The other thing is you’ll really never notice the centering unless the wrapper has a width (fixed/flexible) because at 100% it just fills the screen anyway rendering the effect unnoticeable.
Here’s a little sandbox page I’ve made for my code tests. http://dev.infiniteunreality.com/botp/ It’s a template I was coding for a site I am redesigning (trying to learn PHP templates to do it) and has a bloody mess of CSS in it, but it’s all in plain view to browse through. Also I’ve tested it against IE5.5 to IE8, Opera, Safari, Firefox 3 and up, and Chrome and with some minor box-model quirks, it’s centered fine in all browsers.
The thing I always ran in to with the text-align:center way is that you then have to text-align:left everything else back to get it to look right so I TRY to avoid it since really it’s only needed for IE5.5 anyway.