Also known as a bridge camera or 'superzoom', the the big upside with the power zoom is the lens, which can range to an impressive 20x zoom in cameras like the Sony DSC-HX1 and Canon Powershot SX1. This would usually mean a big, heavy lens on a DSLR.
This isn't without tradeoffs. Light sensitivity isn't as good as a DSLR and at high ISO settings you'll notice image noise sooner. The sensor is also smaller than some high quality compact cameras.
On the other side of the coin, the characteristics of a smaller sensor play to your advantage in terms of convenience. The body itself isn't much smaller than a DSLR, but the physical size of the lens is considerably more compact.
The fact that you can't change the lens limits your freedom, though like Micro Four Thirds, power zooms have the advantage of some fancy image processing not seen in DSLRs - like Sony's Panorama Sweep feature on its DSC-HX1.
|Canon's SX 1 IS has a 1/2.3in sensor, compared with a larger APS-C type sensor in a DSLR like the Canon 1000D.
Power Zoom: the bottom line
Pros: slightly smaller than many DSLRs, big zoom range in relatively compact size, more responsive live view (LCD for viewing scene) system similar to point-and-shoot, some features not found in DSLR such as face detection.
Cons: smaller sensor than DSLR and some high quality compacts, electronic viewfinder rather than the optical viewfinder found in DSLR, can't change lens, bulkier than compacts.
Also in this series, Stepping up to a DSLR camera
Part 2: Should you consider Micro Four Thirds instead?
Part 1: The megapixel myth
Also see our Group Test of 11 Digital SLR Cameras