This has just appeared on the Xbox store (£16.99) I remember loving this and the sequel back in the day. I think I played the N64 version first and then played it again on the Dreamcast.
Here is the blurb showing the enhancements:
Shadow Man: Remastered is a complete overhaul of the classic game with restored, previously cut content!
3 New Levels:
"Summer Camp, Florida" (Day and Night)
"Salvage Yard, Mojave Desert" (Day and Night)
"Asylum Station 2 - Experimentation Rooms"
New Audio (from the original games composer, Tim Haywood):
Remastered music and SFX New music and SFX for the restored levels
Restored cut/unused voice dialog in levels
HD Textures for all levels and objects
Nvidia Intro Cutscene Textures
HD HUD and inventory icons plus a new icon for the Shadow Gun
Restored unused animations
Restored several cut and censored models from the original levels N64 Gad Icons
New weapon wheel to select weapons faster as time is slowed down
Improved destructible objects using Bullet Physics
Levels rearranged as originally intended
A ton of fixes across the entire game to each level from object to geometry fixes
Fixes to the localization for English, French, German, Spanish, and Italian
Over 30 achievements
A second Violator (Consistent with the N64 version)
Sawed-off Shotgun (replaces the second regular shotgun)
New model and many sound variations for the Shadow Gun
Yort Yort Floater
The Seraph Queen
Unused zombie restored in Station 2
One arm Tenement Zombie.
Dynamic Per Pixel Lighting
Clustered Forward Shadow Mapping
New Post Processing Effects:
Depth of Field
Secrets: All the secrets from the N64/Dreamcast/PC included in this remaster Plus many more to be discovered!