At 360g the FZ18 is about 50g heavier than the FZ8, mostly due to the larger lens, but it is by no means a heavy camera. It is nearly 200g lighter than the Canon S5 IS, and less than half the weight of the Fuji S9600. It's also 100g lighter than the Olympus SP-550UZ. It is perfectly comfortable to operate with one hand, although it is certainly better with the two-handed grip that the SLR-like body invites. The handgrip is a bit bigger than one on the FZ8, and with the rear thumbgrip now also sporting a textured surface it provides a secure grip and camera feels comfortably solid in the hand.
It is a well made camera, and despite the low weight the plastic body feels reasonably robust. The battery/card hatch has a strong metal hinge, the tripod bush is steel, and the front edge of the lens barrel has a wide metal rim, into which the lens retracts when powered down, offering some protection to the most vulnerable component. One small criticism of the construction is the viewfinder eyepiece surround which, like the one on the FZ8, is made of hard plastic rather than the more comfortable rubber, and as I found out is quite capable of scratching spectacles.
The control interface is very well thought out. It has the same mini-joystick as the FZ8, which is used for exposure compensation, exposure settings in manual mode, positioning the AF point and also accessing a quick menu system for the main functions including MegaOIS mode, focus area mode, metering mode, white balance, ISO setting, picture size and compression. As a control system it is exceptionally easy to use, and allows very rapid changes to key settings. Other options including flash mode, drive mode, self timer, macro focusing and auto-bracketing are accessed via buttons including the D-pad, leaving the actual main menu for more basic settings, such as the adjustable contrast, sharpness, saturation and noise reduction. One example of well-considered design is the AF/MF button. While all the other buttons respond quickly to a single press, this control, which is positioned close to the shutter button, requires a longer press to activate, so you don't accidentally turn off your AF if you fumble when trying to take a shot quickly.
With such a huge zoom range, the quality of the zoom control is of crucial importance, and Panasonic has made a pretty good job of it. It is operated by a rotary bezel around the shutter button, and it has two speeds. Move the control a little and the zoom moves quite slowly, taking around seven seconds to go from one end of the range to the other, slow enough for accurate framing. But push the control all the way over and the zoom speeds up, getting from 28mm to 504mm in less than three seconds.