I liked it, personally. From what I've seen around here, not many people wanna talk about it, for whatever reason.

Still not up there with the first three games (plus V), but it certainly made up for IV, in my eyes. While it still lacked a handful of things that IV lacked as well, such as character development (though Tactics did a better job than IV, I think), the overall product was a good game, in my opinion.
The skill system worked well, and I liked how certain types of characters even had class-specific skills, such as Deflect Missiles, Armor and Shield Protect, and Smash. It was similar to the skill system from III, which I guess is why I liked it.
The way that support characters worked in Tactics was pretty neat, I thought, and almost all of them were very helpful. (In the end, I think Gary was the main support character I used, for his ATK+ACC boost. Extremely handy.)
Mounts were quite useful as well, especially for the movement boost. The Kangacorn and Giant Owl runes were a nifty benefit to riding mounts, as well.
Many of the characters from IV turned out to be much better in this game (I was quite surprised with Trishtan, for one, and wound up using him for the entire game after I recruited him), and I often had to put some thought into who I wanted to actually use on a regular basis.
The battle ranking was tricky to figure out, as I found myself getting B ranks at an annoying rate. I looked it up online, though, and eventually got the hang of it. If they just provided an explanation for it somewhere in the game (or booklet), it'd be much better, but I still liked it. The way that the Bronze, Silver, and Gold Medals worked out was a bit awkward (Bronze is a better accessory than Silver or Gold, despite being a lower-rank item.

Though Gold and Silver both sold for higher prices, making them better sources of extra cash.), but most of the S-rank rewards were
very nice to have, and worth the effort.
The Quest Guild was pretty standard, but certainly not a bad thing to have. It was a nice source of extra experience and cash, as well as some useful items, and even characters. It was interesting having the competition between Chiepoo's company and X & Co., which added a bit more of choice making to the quests, since the well being of Chiepoo's store affected the items he could sell to you. Most of the quests were rather easy, I thought, but by the time I got up to A-rank and S-rank missions, they did get more difficult.
I thought the story was pretty decent, even if it was basically just a supplement to the weak plot of IV. It certainly did its job in that, and I liked learning a bit more about the Suikoden IV world, since you never heard much about it in IV. The Giant Tree isn't so random anymore, since its significance is explained in Tactics, and it was nice to learn about the Rune Cannons a bit more. (I'm pretty certain that the side quest with Simeon's experiment may have been hinting at the creation of the Pale Gate Rune. It was absent from IV, so it would make sense if the discovery of the Rune Cannons' secret eventually led to the creation of the rune.)
Other details:
I thought the soundtrack was overall well done. I was kind of disappointed that "Rune of Punishment ~Meeting the Cursed Rune~" was only briefly used in the beginning (the original version wasn't heard much in IV, either), since I'm quite fond of that track. The rest of the soundtrack fit the game quite well, though. While it still lacked that Eastern sound that the first two games had, it was still put together well, I thought, and it didn't have me falling asleep during the game.
The voice acting was mostly pretty well done. I found Kyril's voice a bit odd, since he looks way older than he sounds, but other than that, I was content with almost every voice in the game. (By the way, Kyril's voice actor is the same person who did Izzy in the first Digimon anime series. XD I knew I recognized his voice from somewhere.)
(Woah. This is pretty long.
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