iOS (Jailbroken): Sparrow for iPhone was released last week with a slight catch -- it can't handle push because Apple won't allow it. If you're jailbroken, you can easily fix this problem with a free tweak.
Jump onto Cydia and search for "Sparrow Push" to find and install this little adjustment. Once installed you'll be able to open Sparrow and jump into your settings. There you will find a new toggle switch called "Push" which will be on by default. That's all you have to do -- you'll instantly have push notifications in Sparrow. Currently there's no notification centre support, but if you're really aching for push you can at least have part of that functionality now.