Gave StackTrace for iPad a try after I seen @cocoasamurai mention it and have been very happy so far. For a while I would use RSS to follow a few topics on StackOverflow but got tired of Reeder on my phone having an unread badge in the 1000-2000 range.
StackTrace looks good and makes it easy to add tags, search for questions, and favorite a question to view it later. The app is read-only but there is an option to open a question in Safari wehere you could ask/answer a question. Here is the iTunes link for StackTrace if you want to give it a try.