If there was no judder with the old one, and you have judder now, do not look for new faults. The problem lies with the new clutch.
I worked for a major aftermarket parts supplier for many years, 5 of them in the warranty department, and specialised in clutch claims. A few possible causes.
Many people lubricate the gearbox shaft splines, which seems like a good idea, but is actually a very bad idea. Normal grease will fly off, and embed itself into the centreplate lining, which will cause judder. Only a very tiny amount will be enough. Copper grease is worse than ordinary grease. The only cure is a new centreplate. If this is the case, there will be tell-tale slim lines of grease from the centre splined boss outwards to the lining. Only good way to lubricate the splines is with graphite, rub it gently with a soft pencil, wipe off the excess.
The pressure plate is kept in contact with the diaphragm spring by three spring steel strips. If the pressure plate is dropped from waist height, and lands on its edge, the uppermost strip takes all the force, and may bend, losing most of its tension. The pressure plate will then grip the centreplate unevenly during take-up and will judder. With the pressure plate removed, examine the three steel strips, they should all be tight and the same shape. If one is 'S'-shaped, it has been dropped and must be replaced. Reputable manufacturers will replace these, as it could have been dropped anywhere from manufacture to fitment, so impossible to determine blame.
When the gearbox is refitted, it is very important not to hang it on the centreplate. The gearbox must be supported properly until enough bolts have been inserted to hold it. If the weight of the gearbox is allowed to hang on the centreplate, it will bend it. Like bending a piece of paper, it will never recover. As the clutch rotates, the centreplate will flex, and will quite quickly tear itself apart. Meanwhile, it will judder on take-up.
It is important that the gearbox input shaft and the engine crankshaft are aligned. Where the gearbox fits to the engine backplate there will be dowels to ensure this alignment. These can be displaced, or on some, pushed through the plate or casing, so not engaging in both holes. The bolts are not quite as big as their holes, so a little movement can be allowed if the dowels are not present. If the shafts are misaligned the centreplate is running eccentrically to the pressure plate, and will again, tear itself apart. How it tears apart will be different, but the result will be failure. Meanwhile it will judder. This will often give a vibration in normal running too. The wear witness mark on the pressure plate will be a larger diameter than the centreplate.
The shafts can also be misaligned if the backplate is cracked or bent, or if foreign matter gets between the mating faces. This gives a failure similar to the bent plate.
Engine mountings that are worn or soft can also cause clutch judder, but not normally coincidental with a clutch replacement. Main culprit is likely to be the 'dogbone' tie bar at the back of the gearbox under the car, that controls the engine rocking. These do deteriorate, and there are threads on this. It will need checking, but don't be fobbed off as it being the cause in this case. The clutch has to come out again. All mounts need to be checked for correct location and bolt tightness.
Other problems could include driveshaft wear and suspension bush wear, but these can be ignored in this case, as the fault occurred subsequent to clutch replacement.
There could be more, but brain now empty.
