Although I remember loving this game back in the day. I feel this game hasn't aged well. I should explain...
-Often wonky camera. Yes, this IS common in games of this era, but in a stealth game like this you REALLY need to have a good camera, and you don't get that here.
-Stealth levels often devolve into frustrating, tedious exercises in trial and error. Unlike some other stealth games from the era such as Metal Gear Solid and Hitman, being spotted in a stealth section of the game almost always FAILS the mission. This approach to progressing means you'll find yourself getting just a liiiiiiiittle bit further each time in the stealth sections, only to be spotted and have to restart at the last checkpoint. Ugh.
-The game thankfully features analog support, which is nice, but often the controls feel clunky. Especially when messing around with climbing up ledges. This wouldn't necessarily be a problem...in theory. But the harsh penalties for being spotted combined with controls that can make it hard to have precise control over your character add to the frustration.
There ARE some positive things about this game though. The selection of weapons is good, and targeting opponents with the lock-on feature works most of the time. Voice acting in the game is alright and the voices are easy to make out in the mix. Also the cutscenes are animated well by PS1 standards.
But really, at the end of the day the one skill you really need to beat this game is patience. LOADS and LOADS of patience. It's kind of a waste really though, because if you have the patience required to beat this game you should be using it on something more worthy...like learning a musical instrument...or raising kids.