Just installed it without a hitch. I have GTA3 and VC Retail copies. I made fresh installations of both.
I then created a new folder ":\GTALC" I just did a copy and paste of all of my VC directory contents into that folder, then ran the BETA 4.0 executable and pointed it to that directory.
After that, I copied all audio off of my GTA3 Play CD as instructed to the Audio folder contained within my GTALC directory.
No fuss no muss. I even installed the natural HD texture pack. This combined with a sh*t ton of modern anti-aliasing forced by my video card makes this the best looking Liberty City I've seen in some time. Looking forward to adding a bunch of mods and doing a play through.