I had read good things about Movie Studio 11 and decided to try it for myself. It lived up to my hopes and I'd strongly recommend it.
There are several versions. Take a look at Sony's product comparison page before deciding which is right for you, although Platinum is probably the right balance for most users: http://www.sonycreativesoftware.com/moviestudiope/compare
Vegas isn't the easiest video editing product I've used, with a daunting interface, but anyone familiar with free packages such as Microsoft's Movie Maker or Apple's iMovie will find their way around the key areas fairly easily. Once they've done so, it shouldn't take too long to get to grips with some of the more sophisticated features and discover the versatility and power of Vegas. The excellent tutorials make essential viewing and the built-in help is comprehensive.
Maybe you're lucky enough to own a 3D camera, in which case the 3D editing, 3D YouTube upload and 3D Blu-ray authoring capabilities will be valuable. You even get 3D glasses in the box.
Other features are too numerous to mention but the comparison chart (see above) lists them. If all you want to do is chop some of your footage, combine clips, add titles and basic effects, you really don't need anything as powerful as Vegas and would do better with a simpler package. This might be Movie Maker or iMovie (they don't accept AVCHD footage from more-modern camcorders but free converters are widely available). Alternatively, you could pay for Cyberlink PowerDirector which I thought one of the easiest packages to learn despite its strong capabilities.
Vegas ran smoothly on my Win 7 64-bit i7 6GB machine, even though, disappointingly, there's no 64-bit version. I wasn't able to try it on any other PC. Check the system requirements before ordering.
If you're unsure about whether to buy Vegas, get the 30-day trial from the Vegas website first, especially if you have a less-powerful computer. In fact, that's a clever thing to do anyway, because the DVD in the package is unlikely to be the latest build (mine certainly wasn't); install the trial and use the product keys in the package to activate it. You can also download trial versions of competitors such as Corel VideoStudio, Pinnacle Studio and PowerDirector. Me, I've tried them all and will be sticking with Vegas.