I'd go with a metal post. Yeah, i've see a few comments on amazon about the swaying. That would be a deal-killer for me.

I love the feel of my steel Kona H-Tonk and it has the braze-ons for a rack, but the seat stay is really too narrow for a tire over 23mm. The Surly Pacer has a wider seat stay, but no braze-ons for a rack.