You know those 128x128 or 256x256 HD texture packs? They look ugly, IMO.
The textures themselves are actually pretty cool looking, but me being a retro person, I prefer 16x16 and 32x32 textures, and I heard that there was an 8x8 texture out there. I'd like to try that.
Back on topic, HD texture packs, I feel, don't really fit in with Minecraft's blocky appearance. When you see a game like this, you think "retro" or "pixelated" and the default textures were efficient in fitting with this theme. HD textures would only fit when it's a smoothed land and not a system of blocks.
Just my thoughts. What are yours?