Expect to get 10-20 hours of entertainment out of this purchase, unless you can find some friends to play on a LAN - the single-player campaign is extensive and humorous, but replayability is fairly low.
Giants has aged well looks good with any modern PC (minor graphical glitches aside). Even though some basic RTS elements are introduced, the focus is largely on the action.
The game, characters and plot are quite enjoyable despite the slightly frustrating game mechanics and controls. This is a refreshing change from recent games, but doesn't leave much reason to go back and play it again once you've completed the campaign.
The only major let-down during the campaign, the first time through, are four repetitive jetski racing levels during that take about 10 minutes each to complete.