My house was robbed a few years back. We had an active alarm. The thieves were in and out while the alarm was still going, in the morning in broad daylight. They don't really care about alarms, because they, know they can be gone before anyone can respond.
After that I put cameras up. I put them in inside corners facing out of the porches where they can't be walked around, and in other places they can't be reached. This has worked as much more of a deterrent, due (I believe) to the fact that no one wants to be ID'ed while committing a crime. Since a lot of these people are recurring criminals, if you have a good image, your local cops may actually know who they are.
As for what system to use. I've used Zoneminder with IP cameras, and a couple HD USB cameras with powered remote hubs. The IP cameras (foscam) are the most unreliable of the bunch, simply because they tend to cut out when recording an event. You'll get the beginning and the middle, sometimes the end.. but never a full motion event. I've talked to other people and they say the same about a lot of IP cameras. The USB option is great, but there is a limit to the lenght of the USB cable that can be used even powered.