I've ne'er noticed the jerking but I did notice the release on this car compared to my Civic is night and day. I did install the F Sport short shifter and that helped with the throw of the shifter but still don't like the release of the clutch.
There is the F Sport clutch and the Fidanza flywheel if you're ever interested.

 

Digging up an old post in the hopes of focusing on the IS 250 MT problem. I'm a design engineer with enough savvy to be dangerous but not enough to know the answer to our IS 250 MT trans problem.
1.) The problem affects cars in the U.S., UK and Australia.
2.) Dual Mass flywheel contributes to the problem but this type of clutch is used on many high end vehicles and diesels with success. The difference may be (but I have no proof of) is that the springs used are not tuned properly.
3.) Converting to a solid flywheel requires consideration to also convert to a traditional clutch plate that has the springs for shock absorption. Simply going to a solid flywheel will inevitably make engagement rougher and decrease the lifespan of the transmission's other components.
4.) Vehicle's traction control and fuel mapping (torque capacity) contribute to the occurrences of the infamous "Judder" or "shudder". Cold engine, cold engine fuel map, cold engine torque output ALL contribute to a situation where when cold, the problem is worse.
5.) Lexus dealers who claim it is normal, are not being mechanically honest. Yes it seems to be normal to IS 250 Manuals but not normal for most other manual cars. This is code for: They don't have a fix and are unwilling to replace your trans. under warranty because the new one will probably start to do the same thing.
6.) UK and Australian forums have claimed slipping the clutch heavily for a period of time helps "reface" the clutch and flywheel enough to remove glazing and other irregularities that contribute to the judder. Try at your own risk. It may in fact work but hardly the best fix for an expensive car's technology laden equipment.
7.) Bleed your brake / clutch fluid regularly!! System seems (not sure how but it does) to develop air in the lines due to a damper in the clutch actuation system. Damper is designed to "soften" and smooth engagement but can be replaced or eliminated. Air in the lines DOES contribute to the judder.
8.) Change your transmission and rear differential fluid to appropriate synthetic fluid. It helps to reduce judder due to its improved lubricity in cold transmissions and diff's. "Appropriate" means specifically having the right additives for the IS 250 transmission. NOT ALL DO and can cause other problems.

The final word from me is that the IS 250 is a very nice car that is probably a little too smart (fuel mapping, traction control, stability control, and dual mass flywheel) for its own good. They are fighting one another and the result is a condition that could have been avoided using more traditional means (i.e.: solid flywheel & traditional clutch disc).

If anyone has more recent resolutions, PLEASE offer them up, I'm all ears.

 

Never driven the Lexus 2IS manual with dual mass clutch setup; however, I'd not see a big jump up in shifting discomfort if having swapped to a "traditional" clutch setup. Would eliminate those items as the issue. As long as the clutch disk is sprung, transmission components shouldn't see any diminished life expectancy...same with thrust bearings. Have you tried just flushing out the old trans fluid for new OEM? How many qts do one of these cases take...just curious.