I switched to Sparrow on my iPhone full time the night it came out, and haven’t looked back. Yes, even without push notifications, I prefer it over the stock Mail.app.
New features include the Send & Archive action, an built-in browser for links, selecting which mail accounts contribute to the icon badge, and showing/hiding of labels/folders.
They also made mention of Sparrow 1.2. Sparrow’s implementation of Push in their original submission piggybacked on the VoIP API; since iOS apps cannot run in the background indefinitely, Sparrow streamed their mail status over the VoIP backbone and send local push notifications, since this allowed them to exist outside of the 15 minute time limit for background tasks. Apple summarily rejected this implementation since they were not using the VoIP API for actual VoIP.
The developers behind Sparrow explain this in detail here and also discuss the reason that they don’t want to use traditional Push; they feel that email is too sensitive to be passing around that sort of information to a bunch of different servers. Using the VoIP API would allow them to do what they do on the Mac, which is get notifications directly from your email provider without need to pass around authorization credentials. They are confident that Apple will give them a pass on their implementation with this resubmission coming up with version 1.2, though I don’t know if this means they have revised their implementation or if they feel Apple will finally cave.
They do say, though, that should Apple stand strong on rejecting the app’s implementation of push, that they have already started to line up deals with partners to try and bring Push out to the service (Boxcar, maybe?). All I know is that once Sparrow gets Push, my favorite email client will become even better.