Let me set one thing straight, when it comes to brushwork and stuff, I choose hammer over anything else(ESPECIALY Quark.) However, Quark may now be useful for lighting,
Quark recently added real time OpenGL lighting in it's 3d view. I am setting the editor up right now, so I can't say whether it even works with Half-Life, and if it does, whether it is stable. Setting it for HL is a bitch however, as it is intended for old WON/pre-Steam installations.
Also, I can personally atest that Quarks 3d View is click able in Vista, so this may provide a solution for those who have trouble with Hammer, and need to use a 3d view for things like texture tweaking.
Any thoughts? Sounds kinda cool to me.