I've been using Vegas Video
http://www.sonycreativesoftware.com/...egasfamily.asp
http://en.wikipedia.org/wiki/Sony_Vegas for about 5 years.
It's easy to use - I taught someone who'd never used a video editing program how to use it in about an hour - and that included teaching her how to combine and select concurrent footage from multiple independant cameras & combine them into one video stream.
It's powerful.
It doesn't require a mega-machine to run. I run it on a 4-year old PC and it's quite fast enough.
The consumer-level version "Vegas Movie Studio" is cheap, around £30, and a trial version can be downloaded for free. The platinum edition which supports HDV is around £50, and again a trial can be downloaded for free.