While covered well in a few places already, I just wanted to throw in a few thoughts about how the Reading List feature in Lion will affect Instapaper.  I think Marco is completely right not to worry.  There is, however, one area he didn’t seem to address.  

Once Reading List becomes a standard system feature Instapaper will likely no longer be something recommended by Apple.  We’ve seen this with Kindle, now that iBooks is out. Once Apple has an in-house method of doing something they’ll then make that the recommended approach.  This won’t directly hurt Instapaper, but it will remove one way that has helped it in the past.  I suspect when people go into the Apple store and ask about apps they should get on their iPad Instapaper may not be one of them anymore.  

I hope I’m wrong, or if I’m right that it won’t hurt too much.