Acronyms and initials abound for automotive performance divisions. Think about it -- we have AMG, M, S, SVT, SRT, TRD, STI, JCW and so on. Last year saw the introduction of Lexus' foray into this arena with the F performance line. What does the "F" represent? Speculation abounds, but Lexus says it's derived from Toyota's initial "Circle-F" designation of 20 years ago for what would become the Lexus brand itself. It later morphed into Flagship One or F1, which in turn became the internal code for the first Lexus car, the LS 400.

Now that you're set for Automotive Jeopardy, all you really need to know is that the 2009 Lexus IS-F is one ferociously fast four-door. Based on the regular IS entry-level luxury sedan, the IS-F gains all the typical acronym-division performance upgrades, including a muscle-bound 5.0-liter V8, stronger brakes, stiffer suspension tuning, bigger wheels and stickier tires. Unfortunately, many will find the IS-F's fashion sense to be overly flashy considering the company's typical conservatism, and the car's uncompromising ride quality will have even the most dedicated driver considering a lifetime chiropractor membership.

For sure, fearlessly flicking the IS-F into turns is flat-out fun, and the profuse power put forth from the right foot is emphatically formidable. In its own right, the IS-F is a stunning performer. But when stacked up against competing models like the Audi RS4, 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' initial attempt at an ultra-performance sedan, the IS-F is a promising start. But in the meantime, we advise skipping it in favor of one of its rivals.

The 2009 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/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 a six-CD changer, iPod integration and an auxiliary audio jack.

Available options include a 14-speaker Mark Levinson surround-sound system, satellite radio, park assist, adaptive cruise control, and a navigation system with a rearview camera and Bluetooth.

Powered by a 5.0-liter V8 generating 416 horsepower and 371 pound-feet of torque, the 2009 Lexus IS-F rockets to 60 mph in a mere 4.8 seconds. EPA fuel economy estimates are 16 mpg city/23 mpg highway and 18 mpg in combined driving. The only available transmission is an eight-speed automatic with a paddle-shift manual mode.

The 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. Optional safety equipment includes 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.

The 2009 Lexus IS-F is impressive and entertaining 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. The steering is precise and confident when cornering near the limit, although the electric assist does lack a bit of feedback. Thanks to the massive Brembo brakes, stopping power and feel are excellent, halting the IS-F in an eye-bulging 112 feet.

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. Competitors are more fun and refined.

Inside the 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 room for only two rear passengers (as opposed to three seats in the rest of the IS line).