the change:When you go prone there is a period of deviation which prevents accurate aim.
While this may sound like a good idea - stopping the people who jump and prone the moment they see you, it isnt. With the old movement people usually read it - you would often aim low on a person because you just knew they were going to go prone - people adapted to the movement. In a 1on1 fight both players would go prone and a fairrly balanced firefight would ensue.
With the prone deviation it gives advantage to camping - if you sit prone on a hill with a support gun (same for snipers) and someone comes round the corner you have perfect aim, if they go prone for a brief time they won't and they will likely die under your fire.
The effect is it slows the game down drastically, it inhibits the movement of attacking teams pushing forward in favour of those stationary camping in defence. From personal experience I've not just seen an increase in camping defensively but also in the use of support nadespam taking advantage of the slower movements of the attackers. And BF2 certainly doesn't need more nadespam
My personal feeling is that they should have fixed the bugs and cheats, account hijacks etc., and not made significant gameplay changes after almost 4 years. The people that couldn't adapt to the game movement would have left to less jumpy games e.g. cod4, while this change would likely please such people it will not bring tehm back. Those used to the current gameplay and not happy with the changes are likley to find this the final nail in the coffin of bf2