Its a complete scam mate, i wouldnt touch it with a bargepole. By the time you have spent enough money on bidding for the item you rarely get the item for a good deal and in some cases may end up paying a lot more than the item is worth!
I paid 25 pounds for 50 bids in anticipation, I'll be using them wisely, maybe I'll get something, but I doubt it. I think it's just full of bots.
Personally I don't use swoopo but i am building a similar site which is at swipeitup.com What I can tell you about swoopo is that it is legit. they make their money by selling bids, not the product. they have auctions for people that haven't yet won anything. I have done my research of the site and if you bid at the right times and the right part of the day you can indeed win things and get great deals. However, the sites income has to come from somewhere or they'd be out of business. In all honesty you probably won't win the good stuff. However, the system is straight forward and you are no more getting scammed by this site than you would be scammed by a raffle or a lottery.
I have lost some money trying the system out. There is just no guarantee that the system is not fixed. All the owner of the site owuld have to do is create new bidder names and set the "bid butler" to have the last bid. They never actually have to ship a product and every real bidder is left feeling like they JUST missed a great deal. In the meantime, bidders spend $75 each time they try to get the last bid in at the last moment. There is no way to verify anything. There is not even a way to look at the winning history of bidders. The site is geared toward making people click on the bid button as many times as possible. This is the same tactics used by casinos with slotmachines...except in the casino you actually see the money leave the machine.