Well, the Time Machine drive will have to be on HFS+.
For everything else exFAT will do nicely.
I'm not keen on exFAT. It doesn't have redundancy like FAT32.
OS X will write to NTFS via a terminal command.
Yeah I've been using it for years and it's been absolutely flawless. There are some free options too but they aren't as stable. So for the sake of £6ish (at 50% off) to me it's not worth worrying about but if you want to try an alternative:
http://i.vishalagarwal.com/post/30387627819/ntfs-write-on-lion-or-mountain-lion