And despite its stated 8.4-second acceleration from 0 to 60 mph, the 2010 IS 250C doesn't so much leap forward as it gets underway with determination.

On the other hand, most everything else about the test car, a well-equipped IS 250C priced $46,750, was a delight.

Spend weeks and weeks driving $20,000 and $30,000 cars and you find that many are so good nowadays that you begin to wonder what's the point of luxury cars.

Then you plop into something like this Lexus, and realize, ah-hah, there is something extra – quite a lot, in fact – in the best luxury models.

The IS convertible is derived from hardware underpinning the IS sedan. A key difference: The sedan offers all-wheel drive. The convertible doesn't.

Also, the convertible is about 300 pounds heavier than the sedan. But that extra weight is toward the rear, so Lexus says the drop-top has the coveted 50/50 weight balance – half the weight on the front wheels, half on the rears. The sedan is 52/48.

Hard to enjoy the benefits of 50/50, however, when the car's leaning so much in corners that you don't want to drive it hard in the first place.

But back to the exceptional features that make the 2010 IS convertible seem much more upscale than its price suggests.

•Seats were as scrumptious to sit in as they were to view. Somewhere near the best in the business, largely because the lumbar support retracts fully so you don't feel like you have a lumberjack's boot in your back.

•Surfaces were marvelous to see and touch. Rich and rewarding whether eyeing from a distance or fondling up close.

•Noise was mostly absent, which is a tough achievement in a convertible, even though a retractable hardtop allows more sound insulation than a fabric top.

•Shakes and shimmies likewise were all but exorcised, another tough task in a car that has a top that goes up and down.

•Airflow with the top down was well-managed. No air blast or buffet, just a bit of hair muss so folks can tell you've been riding in a convertible. Which is the point, after all. Tall folks might need to hold onto their hats or wigs, though.

•The back seat was tight, but – stop the presses – actually useful. Mainly for kids, though, and chiefly those young enough to be in booster seats. Still, that's more practical than the back seats in most small drop-tops.

The IS convertible is roughly midsize outside, subcompact inside. The top mechanism and storage areas swipe a lot of room behind the seats.

•Top takes about 20 seconds to open or close, roughly half as long as some other Lexus retractables and quick enough to suit most people.

Of course, the car comes with lots of standard features, but these days so do vehicles $10,000 less expensive.

Still, it's nice to know you don't have to go to the options list to get a dual-zone automatic climate control, power everything, deluxe stereo with iPod plug.

Gripes? Beyond the tippy, ponderous cornering feel and the 250's less-than-breathtaking get-up-and-go, not much.

Oh, maybe the price. But if you can afford to be in the luxury market in the first place, the base of about $40,000 isn't so bad for the satisfaction you get, as well as the Lexus hallmarks of presumed reliability and the likelihood of dealer pampering.

There's not much trunk room with the top up due to space taken up by the mechanism for the top. And almost none when the top's down because it stows in the trunk.

The IS 350 convertible, not available for testing, has much more power: 306 horsepower vs. 204 hp in the 250, and 277 pounds-feet of torque vs. 185 lbs.-ft. in the 250. And the 350 weighs only 40 to 66 pounds more than the smaller-engine model, so it should be brisk enough for the enthusiast. Lexus claims a commendable 5.8-second sprint to 60 mph for the 350. Suspensions are the same, though, so don't expect the 350 to handle better just because it's faster.

The reason to balk at the Lexus is the Infiniti G37 four-seat convertible. It has more horsepower, but a little less torque. It's built on a longer-wheelbase chassis and lists a bit more rear legroom, but quite a bit less overall interior space.

The G – not yet tested – promises to handle better. That is Infiniti's forte. The lowest-price G convert is nearly $5,000 more than the low-end IS convertible. But the G starts about $500 less than the bigger-engine IS, a more direct comparison.

Others to consider include the BMW 3 Series drop-top and Audi A5 convertible. If taut driving feel and snappy cornering are important, any of those probably would suit better than the Lexus.

But if hot-shoe motoring isn't that important and real-world comfort is, the Lexus IS convertible is a very, very pleasant car.

ABOUT THE LEXUS IS 250C

•What? Retractable hardtop, rear-drive four-seater.

•When? On sale since June.

•How much? IS 250C starts at $39,815 with manual transmission, $40,985 with automatic, both including $875 shipping. IS 350C starts at $45,265.

•How potent? IS 250C has 2.5-liter V-6 rated 204 horsepower at 6,400 rpm, 185 pounds-feet of torque at 4,800. Available with six-speed manual or automatic.

IS 350C has 3.5-liter V-6 rated 306 hp at 6,400 rpm, 277 lbs.-ft. of torque at 4,800. Comes with six-speed automatic only.

•How big? Midsize exterior, subcompact interior. IS is 182.5 inches long, 70.9 in. wide, 55.7 in. tall on a 107.5-in. wheelbase.

•Passenger space: 87.9 cubic feet. Trunk, 10.8 cu. ft. with top up, 2.4 cu. ft. with top down.

•Weight: 3,814 to 3,880 lbs.

•Turning circle diameter: 33.5 ft.

•How thirsty? IS 250C manual is rated 18 miles per gallon in town, 26 highway, 21 in combined driving. IS 250C automatic: 21/29/24.

IS 350C: 18/25/20.

Burns premium, holds 17.1 gallons.

Trip computer in IS 250C automatic test car registered 19.4 mpg (5.15 gallons per 100 miles) in suburban driving.

•Overall: No corner-carver, but otherwise a sweetie.

Enlarge By David Dewhurst, Lexus The top on the 2010 Lexus IS 250C takes about 20 seconds to open or close, roughly half as long as some other Lexus retractables.