Heyo, just wanted to give a little feedback. Have been running 1.7.3_HD_E2_MT3 for the last couple of days now. All worked fine with HD-textures (varying from 64 to 256); I used the MT-Version because I had pretty ugly graphical glitches with the HD-packs (textures disappeared or flickered) in standard HD_E.
All up until now... I started to build pipes with BuildCraft. Now, in the area around the pipes textures are simply gone. Not everywhere, but always. You can see on the picture.

The pipe should go down the line across the water where the two dirt blocks are seen. So these aren't rendered properly at all.
The HD-textures have no influence on this, aswell as the settings. After different tests I discovered, that everything renders fine with 1.7.3_HD_F. HD_F_MTL and HD_E_MT both have the rendering problem. The flickering with non-MT is gone in HD_F on the other hand, so this isn't as much of a problem to me.
Still wanted to say, that there still seem to be some glitches in MT. Apart from that the MT ran very well on my PC with Dualcore and Nvidia GTX560ti.
Keep up your great work. Without it MC would be a horror to play!