There are countless of live & successfull solution built above / with SharePoint.
As soon as you have collaboration needs, document management requirements, workflows, search, external services integration, etc. you'll find real world case studies described in these 200+ list : http://www.microsoft.com/casestudies/Case_Study_Search_Results.aspx?Type=1&Keywords=SharePoint&LangID=46.
Regarding your query, you can customize an existing site template for your HR needs like the ones listed here : http://www.microsoft.com/government/en-us/campaigns/pages/sharepoint-templates.aspx
Employee Activities Site The Employee Activities Site application
template helps departments, such as HR and marketing, to manage the
creation of and attendance at employee events.
Employee Training Scheduling and Materials The Employee Training
Scheduling and Materials application template helps instructors to add
new courses and to organize course materials. Employees use the site
to schedule attendance at courses, to track courses they've attended
and to provide feedback.
Absence Request and Vacation Schedule Management The Absence Request
and Vacation Schedule Management application template helps
departments to manage requests for out of office days and provides
dashboards showing which users are assigned to each set of
Event Planning The Event Planning application template helps teams to
organize events efficiently through the use of online registration,
schedules, communication and feedback.
Resource Availability Site The Resources Availability Site application
template helps users view, manage, track, and approve resources.
And for the survey need, you can create survey lists based on your requirements.