We last covered the iOS RSS reader Byline back in May of last year, when it had just hit version 3. Now the app's been updated to version 4, and it's still an excellent RSS reader for both the iPhone and the iPad. Version 4 brought universal capability to the free version of the app (it has ads, though you can get rid of them for just a few bucks). The new version also adds an easy way to "Mark All as Read" (just slide the "Edit" button), and the 4.0 release (as well as the minor releases after it) fix all kinds of bugs and add in some performance improvements.
Byline still hooks up directly with your Google Reader account, integrates with Instapaper and Twitter very easily and has an offline reading mode that lets you browse your RSS feeds even when you're not connected to the internet.
In other words, Byline is a quality app that's only getting better. If you still haven't settled on a good RSS reader for your iPhone or iPad, it's definitely worth a look.