partition plan

I'm hoping to install Ubuntu Linux soon. Could you check my partition plan?

OS-Data Type File Size (GB)
Windows XP Physical ntfs 10.00
Ubuntu Linux Extended 18.00
     /(root) Logical ext3 0.50
     /usr/ Logical ext3 4.50
     (reserved) Logical ext3 13.00
Shared Data (/home/) Physical ext3 90.00
Swap (/swap) Physical ext3 2.00
                                           TOTAL 120.00

1. Did I set aside enough space for / (root) or is it too much?
2. Do I need to reserve a separate partitions for /boot and /var if I will only use Linux for personal use (audio & video, games, office)?
3. To minimize problem in future upgrade, or to avoid crashes, what else should I consider?