I started the series with the original, ie STW, and played till RTW before quitting.
The people who complain about MTW are those who started playing the series either with STW or MTW. In a way, that tint their glasses when viewing later games, but there is perhaps some truth to it, and it stems from RTW.
For those who played STW or MTW first, they will appreciate the effects of terrain, weather, overcrowding, since these can make or break a battle. In RTW, the effects were lessened (overcrowding penalties were even removed) and units seem to have grown bionic legs. Cavalry charges became extremely powerful and one can easily win by getting a large number of cavarly, select them all, and them have them charge at an enemy unit, rout it, then rinse and repeat. Most of the veterans denounced these changes as CA selling out for the "RTS" crowd. Of course, patch and other issues created further bad blood between the "veterans" and CA.
Later came M2TW. Some of the worst excesses of RTW were toned down (cavalry charges are now harder to accomplish, but some call them bugged instead) but some still feel it being a little arcadey. Of course, M2TW has its share of issues that do not help.
Other things that people missed from include titles, civil wars and the GA mode.
For the faction placements in MTW, they were done to reflect history, not to make things easier for the player.
As for the original MTW running on XP, most of the problems seem to be related to Nvidia 8000 series cards.
