Below listed are the some of the components you can check on.
User end:
- Check if all portals/web applications are responding fine.
- Email Enabled Lib/list.
- Workflows.
- Alerts.
- Add, update, delete list/ lib.
- Add, update, site with Branding (if any).
- Add, remove permisisons.
- Clear recycle bin.
- Check Site Auditing.
- Check Manage Content and Structure.
- Excel Services.
- Infopath Forms.
- Mobile/Blackberry access.
- Outlook Synchronization.
- People picker.
- Central admin access
- Create Site Collection.
- Delete Site Collection.
- Update Site Collection.
- Modify Site Collection admins.
- SSP access.
- Start/Stop/Pause crawls.
Hope this helps you all.