It's a good place to wander, take in the sea air and gaze at the views - with the aid of a telescope if you have a few dollars on you. There are seats scattered about so you can admire the action ranging from cruise ships and the Spirit of Tasmania coming and going at Station Pier, through to tankers and yachts crossing the bay as well as the views across to Williamstown and the Westgate Bridge. The old pylons that remain at the end of the pier are definitely a photo opportunity.
Constructed between 1912 and 1915, Princes Pier was the site from which many Australian troops set off for the first and second world wars. It also welcomed troops from the USA during the second world war as well as many migrants from around the world who came to make Australia home. The pier was originally called 'New Railway Pier' however it was renamed in 1920 in honour of the royal visit by the Prince of Wales.
While there isn't anywhere to buy food on the pier at the moment (though you can always bring your own) there are cafes and restaurants on Station Pier and in Beacon Cove and nearby Bay Street, Port Melbourne has a wide variety of eateries.
If you're looking for a "bayside" day out this area has a lot to offer. As well as exploring Princes and Station Piers, there are cycling and walking tracks along most of the foreshore, some good beaches and lots of things to do and places of interest in Port Melbourne and surrounds.
Tram 109 lightrail takes you to Port Melbourne (closest stop to Princes Pier is Stop 129 for Beacon Cove/Station Pier/Cruise ship terminal). If travelling by car there's ticketed parking on Station Pier and some free and ticketed street parking in surrounding areas.