You can use Street View in the Maps app; at least until iOS 6. Then Apple will stop using Google for their Maps app.
Originally Posted by Commodore
To use Street View, tap and hold near the street you want to view, until a purple pin drops in place. Tap the pin. If Street View is available in that location you'll see the orange Street View icon at the left of the pop-up will be bright. Tap it to enter Street View. Or you can tap the blue (i) con for info, and then tap the Street View thumbnail that appears.
It sometimes take the app a few seconds to highlight the Street View icon.