Hi,
I want to hear some opinions about what you do after installing a basic Solaris8 on sparc. What customizations you do? What you tune?
1.Mirroring disks.
2. .....
3. .....
etc
Thanks in advance.
Pretty much depends on what you wanna do on this system.
The last things I made on t1000 server were :
shell change, root pass change, new sshd options, allowed/denied services, one user added, new path credentials added + export, added extra disk, configured ALOM, verified its functionality, edit of /etc/profile, bash_profile, ulimits, new start-up scripts, stopped unused daemons, echo-ed new TCP / kernel parameters, and many more 
That actually depends. Where I work, we install using jumpstart and the image is already customised to confirm to the guidelines that we follow. There are a lot of things that are done, right from blocking telnet, to a customised banner message...
As it would be in most (even small scale) business/enterprise deployments. The emhpasis is on three things in these setups:
- Removing user steps ( less error prone )
- Standardisation
- Repeatibility
If you know what you are doing, you can do just about any customization from jumpstart, including disk mirroring etc.
In terms of what we(I) customise where I work ( all from jumpstart ) not all always apply.
- Disk layout and mirroring.
- Services.
- Network config.
- Root password
- SSH config
- Users
- NFS v4 domain
- Secondary and teritary Name services
- Sendmail
- Patching
- External mounts
- Power Management
- Dump devices
- In-band management for Storage
- Cache Controller parameters for exteral DA storage