External Drive with FAT32 - issues?

I purchased a Seagate 300 GB external drive a few weeks ago and transferred all of my data from my smaller external and gave it to my girlfriend. Since then I have transferred several other large important files and finally got around to reading the manual.

The manual states that Mac users must format the drive before using it because FAT32 is not recommended. I wanted to be able to interchange the drive to transfer data to my friend's PC so I never really thought about formatting (the box says it's ready to use on Mac and PCs). It has been working fine on my eMac (10.3.9). I now have no place to put my data to enable me to reformat the drive, short of buying another external (and maybe returning it shortly after). Does anyone know if I will run into issues later and pay for my carelessness?

All I have overturned is that OS X cannot mount a FAT32 over 137 GB, but it mounts just fine.

Any advice, statements concerned impending doom, or information would be much appreciated. Thank you!