This constant swapping of class types has obvious benefits (everyone could have totally different parties saving the world), but it also contributes to the overall annoyance you'll feel while playing. Anytime you switch classes, there's a gap of "x" number of battles where that character isn't fully integrated into the role and is weakened. Like-themed classes transfer faster (two to three battles) while drastically different or untouched classes can take up to 10 slow-paced random battles to change. Every time. Ugh.
The process can take so long that the game's approximate length (we're calling it at right around 30 hours) is bloated with leveling up and strengthening your various jobs. Then you realize you're never sure which jobs are absolutely crucial for success in a given cave (one fight demands dragoons, another a dark knight) so you could have easily spent 30 minutes leveling up a class you'll never need. It all boils down to hours upon hours of fighting the same monsters over and over.
Think it can't get more obnoxious? Oh, it can. Caves, dungeons and the like have no save points or way to restore your health and magic points. You've either got to nail the whole area in one run (not likely with the frequent battles) or head in a few floors, warp out and heal, head back in and repeat. One section near the end even has you fighting two bosses back-to-back after a tremendously long haul, with no opportunity for healing in between the fights. It's accurate to the original version, sure, but we'd be lying if we said we didn't want to take a bite outta the damn DS after dying repeatedly.