BidSlammer has all the features you could want in a sniper and is still super easy to use. I especially like the slam-it tool bar. You can find the item you want on eBay, click the slam it button, enter your bid, and you're done. Couldn't be easier! There are also several other useful features like bid groups and importing your watch list.
Security is great as the entire site runs in HTTPS. Once you are logged in every page you visit is secure. The service is reliable and user friendly. I would definitely recommend it to others.