Really? You had to port this to the original PlayStation? Why? While the controls are decent, this is a porting disaster that cannot be considered one of the PS1 Greatest Hits. And apparently, it was very questionable to include itself on PlayStation Classic, and even worse that version has an error that basically makes it unplayable. At least it's the only Rainbow Six game before Rainbow Six 3 that shows the weapon being held in the player's hands.
The graphics are hideous and terrible. No, really, it's even worse than early PlayStation games. The textures on the models are hideously deformed. The color palette is low. The character animation is poor. Even the frame-rates are low.
It has lots of bugs and glitches, with your operative frequently getting stuck in doors or being forced to crouch to get through a normal-sized door opening. Also, ridiculously poor enemy AI: if you strafe, they don't shoot at you, except if you stop strafing, and on hard difficulty, they kill you immediately.
The levels are so poorly designed that enemies frequently blend into the background, making it difficult to shoot. In addition, the option to plan out missions manually, a major feature of the PC version, is removed. There are also missing briefing dialogues and inconsistent briefings: some levels have incorrect time of day when you get to the actual level.
What is even the worst aspect is that there's no multiplayer or co-op modes! I can't think of anything else positive to say here. I'll say that at least the PC version is outstanding...