This was my second time playing through it, as I beat it back when it was originally released. My save file says it took me 23 hrs to beat (plus maybe a couple hours of restarts due to one death, checking out different options, or going for a better rating against a boss). I missed a few things, but I got the second highest rating that it gives, which is based on completion percentages.
First and foremost as to why I give this a 10/10 is the battle system. To me, it manages to keep the feel of the two rail shooters released prior to this, which are both among my favorite games. It also has one of my favorite video game soundtracks. The ability to modify your dragon's strengths and weaknesses at any time, once you gain that ability, is really nice. I like that you get more Exp and Dyne (currency) depending on how you perform in each battle, which gives you an incentive to try to be the most efficient.
On a second playthrough, the magic of that first experience was gone, so places like the Uru Ruins and The Tower did drag this time. There are very few places to go with only one real town, and only 3 places outside of camp with any real character interaction. Several of the hidden items are buried behind repeatedly talking to people a LOT, plus some items are missable if you do one thing out of order, so these could be drawbacks if you want to get everything -- but these missable items won't prevent you from 100%-ing the game for the purposes of getting the best rating. For such a small game world, there are quite a few hidden things. There are a handful of places where there is noticeable slowdown, but nothing horrible.
I have a High Performance brand memory card, and the game will not load a save game from the card, although it will save it to it even though it doesn't show the save data. I'm not sure if it's the brand of card, as I've never had a Sega brand card to test it out. I also had one spot of skippable dialog in Camp late in Disc 4 where it would skip like a broken record and cause the game to freeze, but I was able to just skip through the text instead, which disables the voice for that segment. I seem to recall this happening when I played it the first time, and I bought it new, so it might be a game issue.