ROM 4.00.01 and aboveon XDA: need advice

[gabbaid]

I am currently using WM2003 with ROM version 4.00.01 & Radio Stack 4.21 from O2.

Is there any need to upgrade?

I saw around ROMs up to 4.00.16. Can anybody tell me the difference?

Also any reason to update to Radio higher on Vodafone Italy network (900/1800)?

Thanks

Daniele