This is luckily true, even for watching local 1080p-content with 1GHz-PC/AGP4x-Bus and proper AMD/ATI-GraCa, but streaming is NOT working properly with MPC-HC. For this, of course vlc is best !!!
I'm using (K)ubuntu 10.10/2.6.35 and vlc 1.1.4 for watching http-SD-TV-streams on that "Oldy", streamed by HT-PC with DVB-S2-card - this is a perfect show compaired to XP-performance on same PC( . . . even XP-SP2 exhibits some frame-loss with 8Mbps-mpg-streams on my setup) !
Hopefully HD-performance of vlc for XP and Linux will improve in the future, perhaps at first Linux-developers can agree upon a system-wide VideoAccelaration-interface to be used by any "open-source-player".
Edit 10.3.2011:
viewtopic.php?f=14&t=79953
. . . starting "GPU-accelaration(experimental)" for AMD-hardware shows no effect with vlc1.1.4 and Kubuntu 10.10 using "standard"-setup. One has to use AMD's "restricted" fglrx-driver(recent version 11.2:
http://support.amd.com/us/gpudownload/l ... ng=English) and missing libxvba-something(for Ubuntu/natty) for this ?