The 4-pound Sony VAIO VGN-SZ791N falls somewhere between a beefy ultraportable and an all-purpose laptop.

Thanks to its Intel 2.5-GHz Core 2 Duo T9300 CPU (a Penryn-class processor that we see in some desktop-replacement notebooks) and its nVidia 8400GS graphics card, the SZ smoked our WorldBench 6 performance tests with a score of 94. Among all-purpose notebooks, even Lenovo's ThinkPad R61 and Fujitsu's LifeBook A6120 couldn't match that number.

Aside from strong performance, this laptop has several likable features. Two customizable shortcut buttons sit at the top of the keyboard. You can use them to call up a number of useful functions--multiple monitor mode, hibernate, brightness adjustment, or a snapshot look at key notebook functions, for example.

The SmartWi wireless utility is a quick diagnostic tool for toggling such options as Wi-Fi, Bluetooth, GPS functionality, and integrated wireless WAN (through Sprint Mobile Broadband). A goofy little Wi-Fi antenna that sprouts from the side of the notebook provides a slight barrier between the keyboard and display, and may guard against minor dings and nicks.

The 13.3-inch screen (with crisp 1280-by-800-pixel-resolution) is vibrant and easy to view from various angles. Though not as gorgeous as its sibling, the backlit VAIO VGN-TZ295N, the VGN-SZ791N does the job. The display's aluminum backing gives the notebook a substantial feel, as does the smooth metallic wrist rest.

Unfortunately, the keyboard is uses a shallow plastic casing that cheapens the typing experience. At least the keys are sufficiently far apart that you won't slip and hit the wrong key.

The laptop's worst feature is its mouse. Huge gaps act as trenches between the loosely fitting left- and right-mouse buttons  and the case. While trying to left-click, I occasionally caught my finger in the chasm.

A power management toggle lets you switch between speed and stamina modes (the latter promising to support 3.21 hours of work). Such toggling is handy for simple settings, but why must the laptop restart?

The SZ791N's power is undeniable, but the keyboard and the mouse buttons raise questions about component quality. And considering Sony's $2500 asking price, we can't help but wish for a little more.