To 64 or Not to 64?

[David Baron <d_baron@012.net.il>]

I am currently running Sid, 32-bit with recent i686 32 bit kernels.
Here is my cpu: ~$ lscpu
Architecture:          i686
CPU op-mode(s):        32-bit, 64-bit
CPU(s):                2
Thread(s) per core:    2
Core(s) per socket:    1
CPU socket(s):         1
Vendor ID:             GenuineIntel
CPU family:            15
Model:                 4
Stepping:              3
CPU MHz:               3000.282
L1d cache:             16K
L2 cache:              2048K

Should I go to a 64-bit kernel? Benefits vs. Risks?
Will 64bit enable kvm functionality on this box?

Will this work with existing packages which could then be changed to 64 bit 
piecemeal or if taking the plunge, must/should redo everything?