Summons : There are two forms of summons, Arc's Summons are the Guardians of Light, Fire, Water, Earth, and Wind. Over time and experience they'll grow in power and range.
Chongara's Summons are actually his Magic Skills, he has Kelack, Mofly, Odon, Hemo-ji, Rai-jin, Fu-jin, & Choko. Each will act as an additional character in battle.

Spells/Skills - Each character has their own unique skill. Arc can summon Guardians to cast powerful spells.
Kukuru can cast magic, mostly healing magic.
Poco can use his band intruments to act as support or attack skills.
Gogen is a heavy spell caster he uses mostly offensive spells.
Chongara summons additional characters to help out, he also has a Search ability that can be used on monsters to find out their stats. By Pressing select you can look at the Monster Book to see the collected data.
Tosh is the samurai of the group he uses special sword related attacks.
Iga is the monk/fighter of the group, his skills relate the spiritual fighter's method.
Each Character's skill starts at a low level, but it can grow in power and range through gaining levels. The max Level you can get to is Lv60.

Gameflow - There's 3 main areas you can navigate, there's the Continent Map, which lets you select an area to visit wether it be a battle zone or a story advancement zone. The 2nd area is the Zones, the Battle zones are marked in red, you enter them and are immediately taken into a battle. The Story zones take you either into a town/castle/dungeon to advance the plot, or you can alternatively re-visit one. The 3rd area is the world map which lets you select which continent you are going to visit. The Airship will fly in the background of the World Map.

Side-Quests - Theres about 3 that I know of; the first is to Win 1000 battles in the Tournament to get a special item. Second is to get Choko from the Forbidden Ruins, you'll need to go down through 50 floors, without saving, defeat Choko, then make your way back up through the 50 floors and exit. The 3rd quest is to defeat an amount of enemies in Zaraban Desert to get Poco's final skill, It was 80 I think.

Music - The music is great, but if you're in one too many battles you can quickly get tired of the battle music. The opening intro music is the best. Too bad there's no soundtrack though.

Fun - When I was looking around the net wanting to know what Arc the Lad was like, I got the impression it played like FFT, which in some form it does. It took some getting used to, and even though normally you'd only be playing for 10 hours, I took an extra 10 hours to play even more, so yeah this game was fun to play.

Buy VS Rent - Well I really doubt you'll find this in a game rental store, so I'd say buy Arc the Lad Collection, a series that takes 160 hours to complete. I heard that SamGoodey had it for $20, saw that EBGames had it for $50, Toys R Us had it for $70, I got my copy off ebay for $48 (thats with shipping), so I think your best bet is ebay or a local gaming store.