It gets tougher, especially if you're going solo. I'll admit, it's difficulty is nothing compared to a normal ff though. I never really got to play with more than 2 people, which is a shame.
Single player is both more difficult and easier than multiplayer. You have access to magic you can't use in 2-3 player, but not 4 player. As well, if you don't have a phoenix down taking up precious space, death is death..
It's fun, the last area is hellaciously hard though. More than the standard FF games last areas.
I had never played it just because I heard single player was balls, until last Summer. I played it a few times with Sabs, Palum, and Dugrasse. I had a lot of fun playing, and every once in a while I get a craving for the game and want to play.
It's a very fun game if you can get more than 2 people to play with you. I used to have family come over every sunday and 4 of us would plug in our GBAs and play for hours. Then TLoZ: FS came out, and we played that profusely. Damn, those were good times.
My friend and I both played this game together when I was at his house for a week a couple summers ago. It was a lot of fun playing multiplayer, and although there's not too much to it, it still has a good story to it when you get to the end, and the gameplay is quite fun.
My main beef was that it required a gameboy and the cable to play it...sure the radar etc was handy but in my opinion just letting you use a controller would have saved alot of hassle and made the game more widely avaliable for people to play.