i currently use Viigo (
Download | Viigo) for my BB Curve. problem is, i don't think it's an iPhone compatible app. hopefully they will introduce a version for iPhone because you can setup any rss feed. just like a google reader.
i HAVE, however, seen an rss reader in iTunes called 'NetBeans' that limits you to what seems to be 2 rss feeds and very little in customization of specific feeds. i just downloaded (via iTunes) an app called 'NetNewsWire'. it's a free rss reader app that looks descent. there's also one called 'Gazete', but the reviews were mediocre at best.
now, i just need to get my 3GS to try it out...27 more days. ARGH!