Which are main technical reasons to switch to Lion? Everywhere I just read posts and questions about how to make lion like snow leopard.
So... Why not keeping snow leopard, at least while lion's "young"?
Are there any technical / cosmetic reasons for the switch?
Lion's improved security is worth a mention. Don't get me wrong, Lion still has its share of security issues (see LDAP and enterprise updates).  But Apple's inclusion of sandboxing, full hard disk encryption, and a better ASLR goes a long way to reducing exposure to a wide variety of attacks.