Well since I had my first BlackBerry there has been a slew of RSS readers that have come out one after the other. The most recent I have discovered is called FreeRange. This is actually the software that NewsGator To Go is based on. The software is Free for up to 10 feeds and has a premium version if you want more. Personally I use Viigo just because it is completely free but I know the readers of BerryReview are all about trying every application. FreeRange has a BlackBerry client that can be installed OTA and works like a charm on my BlackBerry 8800. Just like Viigo, FreeRange is designed to also be used offline and stores the RSS feeds locally.
There are certain features in FreeRange that give it a lead over Viigo. For those of you who use Google Reader there is a nice integration option built into FreeRange. Also personally I think the browser integration is much better for viewing the full article. Last but not least Viigo does not give you any options when it comes to images. It auto-thumbnails them but FreeRange also allows you to zoom in for a better picture.