Pour yourself (or your kid) a bowl of Alpha-Bits cereal and chances are you'll see almost every carmaker's ultra-performance division -- AMG, M, RS, V, SVT, SRT, JCW -- spelled out in your milk. A couple of years ago, Lexus joined the acronym club with the introduction of its F performance line. Though most car nuts can give you the meaning of the other brands' initials, one may wonder what the "F" stands for in regard to the 2010 Lexus IS-F. The official explanation relates to the company's internal code for its first flagship Lexus model, the LS 400. But all you really need to know is that this is one ferociously fast four-door.

Based on the regular IS entry-level luxury sport sedan, the IS-F is fortified with all the expected "performance division" upgrades, such as a tire-burning V8, bigger brakes, stiffer suspension tuning and stickier tires. You also get sport front seats out of the deal along with the IS's already high-quality cabin. Sadly, and out of character for typically conservative Lexus, the IS-F also sports somewhat juvenile styling tweaks and suspension calibrations that all but guarantee a professional relationship with a chiropractor.

Make no mistake, the IS-F is a serious machine that will quickly slice through a curvy road and pin you to the seat when you pin your right foot to the floor. In terms of numbers, there's no denying that the 2010 Lexus IS-F is a stunning performer. But when compared to models like the BMW M3, Cadillac CTS-V and Mercedes-Benz C63 AMG, it comes up short in terms of real-world usability and overall satisfaction. As Lexus' first attempt at an ultra-performance sedan, the IS-F is a promising start. But in the meantime, we'd rather have one of its more well-rounded rivals.

The 2010 Lexus IS-F high-performance luxury sport sedan is available in only one well-appointed trim level. Standard features include 19-inch alloy wheels shod with sticky tires, Brembo brakes, adaptive xenon headlights, a sunroof, keyless ignition and entry, auto-dimming mirrors, 10-way power heated front leather sport seats with memory settings, dual-zone automatic climate control and a 13-speaker audio system with satellite radio, Bluetooth audio, a six-CD changer, iPod integration and an auxiliary audio jack.

Available options include a hard-drive-based navigation system with a back-up camera and real-time traffic and weather updates, a 14-speaker Mark Levinson surround-sound system (you can only get it by also ordering the navigation system), park assist and adaptive cruise control. Navigation-equipped vehicles come with a one-year subscription to Lexus' Enform, which provides on-call travel advisers who can help drivers with destinations (e.g., a movie theater or the closest gas station) and then send the info to the navigation system.

The IS-F is powered by a 5.0-liter V8 generating 416 horsepower and 371 pound-feet of torque. All that power is sent to the rear wheels via an eight-speed automatic (with a paddle-shift manual mode), which is the only available transmission.

With the ability to rocket from zero to 60 mph in under 5 seconds (4.8, to be exact), the IS-F is indeed in rare company. EPA fuel economy estimates are 16 mpg city/23 mpg highway and 18 mpg in combined driving.

The 2010 Lexus IS-F comes equipped with antilock brakes with brake assist, stability control, traction control, front-seat side and knee airbags and full-length side curtain airbags. There is also a one-year complimentary subscription to Safety Connect, which provides collision notification, stolen vehicle location and an "SOS" emergency help button. Optional is a pre-collision system paired with the adaptive radar cruise control that senses an impending collision and automatically adjusts seatbelt tension and braking force.

The IS-F has not been crash-tested, but in government testing, its IS 350 sibling was awarded four stars out of five for driver and front passenger protection in frontal impacts as well as rear side impacts. In front side impacts, it was awarded a perfect five out of five stars. The Insurance Institute for Highway Safety gave the IS 350 its top rating of "Good" in its frontal-offset and side impact tests. Thanks to the massive Brembo brakes, stopping power and pedal feel are excellent, halting the IS-F in an eye-bulging 112 feet.

The 2010 Lexus IS-F is impressive and entertaining from behind the wheel. Halfway up to the 6,800-rpm redline, the throaty V8 unleashes a grin-inducing roar. Grip provided by the sticky tires is up to the task of handling the athleticism of the chassis. The steering is precise and confident when cornering near the limit, although the electric assist does lack a bit of feedback.

If prodded, the IS-F will lay down rubber in a torrent of billowing white smoke until the tires self-destruct, provided you turn off the electronic stability control. Although we'd still like to see an option for a traditional manual transmission, the eight-speed auto is definitely well suited for racetrack duty, thanks to its super-quick upshifts and rev-matched downshifts. Likewise, the super-stiff suspension is ideal for weekend track-day use.

On public roads at legal speeds, the IS-F shows its flaws. With so many gears, the transmission seems to be perpetually searching for the right ratio. The rock-hard suspension is too rough for everyday use, sending Richter-scale shock waves directly into the spines of the occupants.

Inside the IS-F's cabin you'll find top-quality materials, superb sound insulation, well-placed controls and a trunk pass-through -- much like in the IS 350. To its detriment, the IS-F also inherits the 350's limited headroom and rear-seat legroom, which proves problematic for adult passengers -- particularly taller ones. Setting the IS-F apart from its less exotic brethren are aluminum trim pieces, ambient lighting in a soothing blue hue, sport seats and a backseat built just for two rear passengers (as opposed to the three in the rest of the IS line).