I too did notice strange stuff as explained by Phillip with the bigger planes, especially 747, 777 and 767, and also A340. Did not try with A380 as yet (offline)
What I usually do is try and line up with the runway much much earlier than required (wherever possible because of terrain too) and ensure that all my 3 systems, altitude, speed and heading is managed by the autopilot. Once established on the localizer, I check myself again by pressing the approach option and if plane is not behaving or turning violently, I leave it running or resort back to handling using heading autopilot. I always do a lower than glide slope approach, it helps me to correct quicker if necessary than being too high to land!!
But most of it all, its the weight of the aircraft that matters. I do notice that FS plays around with weight at bit and shorter flights of FS with full fuel can be a big culprit. Second is the speed, if you have more than half the fuel, then land somewhere around 160, else make it on 150. Since you are lower than glide slope, touchdown tends to be a little more smoother as on power I hover the plan till the threshold of landing is reached. Then a quick flip of the autopilot, and the plan touches down smoothly.
All said and done, I do notice one thing - thats called ANXIETY.... whenever I come to land when playing online on Vatsim, my heart beats much faster, touches close to 90 instead of 72 bpm and I tend to do a harsh landing ... Now I keep practicing landing in the airport and practicing my flight plan from the area when I need to fall below FL100 and then only do the real live stuff.
Hope this helps!!
