Not one of the best in the series, but still quite good despite some flaws.
I'm just going straight to the weak points. Firstly, I don't like the magic junction-system. It becomes just too big a micromanagement task to junction all of your spells in to appropriate attributes. The junctioning isn't the biggest problem though. The real problem is gathering the magic to junction. This is done with the draw function in battle (and with GF abilities, though more useful later in game) and it takes a lot of time to draw enough magic to make the whole drawing process worth while. If you attempt to avoid the busywork that is drawing magic, you often find yourself with too few spells to use. I have to admit though, that the feeling you get after drawing 100 (which is the biggest amount you can draw each spell) spells is nice. But when you realize you must do this for every spell and for every character for your party to be effective, it quickly becomes work.
Other complaints you hear about this game are that the plot makes no sense, is too centered on the lovestory of Squall and Rinoa and that there are many plotholes. Some people feel strongly about the weakness of the story in this game but I can forgive some flaws; you shouldn't always observe the plot's little details with a magnifying glass. I have my limits too though. When you play this game, there will be some "WTH?" and "Are you serious?!" moments because of the plotholes. The first disc is ok, but after that things start to get weird.
Sidequests. FFVIII has a card game named Triple Triad which seems to be the biggest sidequest thing to do. I didn't like it but that's just my personal opinion. The appearance of it was disappointing and the regional rules made it confusing and sometimes annoying. There is also chocobo-related activities but it's centered around a tamagochi thing for which you need a Pocketstation which isn't / wasn't available anywhere but in Japan.
This game isn't all bad though. The music is good as you'd expect from Nobuo Uematsu. Has he ever gone wrong? The boss battle theme and "The Man with the Machine Gun" are two great examples of the good music this game contains.
The battles are often fun and the summons animations are beautiful. The GFs' boost feature (pressing repeatedly square-button to increase damage) becomes tiring after a while and I am glad that I have a macro-feature on my controller and I never had to force my arm to cramp up.
The visuals are also great for its time and the CGI scenes look good even compared to today's standards. The animations are great, they don't look bad at all.
As a conclusion this game is good but not one of the best in the series. If you are a FF fan that is yet to try this game, I say go ahead. It's a fun experience despite its flaws. If you're a person who wants to buy his/her first Final Fantasy, I have to say don't start here. Take VII or IX instead. VII is a classic and IX is a great tribute to all the past Final Fantasies.