Aaron Margosis has excellent set of posts on why and ho to run as LUA (non-admin). If you wander what's in it for you or have particular problem while running as non-admin, you owe it to yourself to read his blog.
Here's a short list of Aaron's posts on the topic:
First the “Why” posts:
Why you shouldn't run as admin...http://blogs.msdn.com/aaron_margosis/archive/2004/06/17/157962.aspx "Zero-day" attacks and using limited privilegeExpect to see more malware predating the patches - and how you can protect yourself. (Or, "Why you shouldn't run as admin, Part 2")http://blogs.msdn.com/aaron_margosis/archive/2004/06/25/166039.aspx
Why you shouldn't run as admin...http://blogs.msdn.com/aaron_margosis/archive/2004/06/17/157962.aspx
"Zero-day" attacks and using limited privilegeExpect to see more malware predating the patches - and how you can protect yourself. (Or, "Why you shouldn't run as admin, Part 2")http://blogs.msdn.com/aaron_margosis/archive/2004/06/25/166039.aspx
And then the “How-To” posts:
The easiest way to run as non-adminThis is the really important one for your non-techie friends and relatives ...http://blogs.msdn.com/aaron_margosis/archive/2004/06/17/158806.aspx "RunAs" basic (and intermediate) topicsA whole lot of detail about how to use "RunAs" to run programs under a different account.http://blogs.msdn.com/aaron_margosis/archive/2004/06/23/163229.aspx RunAs with ExplorerHow to get Windows Explorer to work with RunAs (and why you might want to).http://blogs.msdn.com/aaron_margosis/archive/2004/07/07/175488.aspx MakeMeAdmin -- temporary admin for your Limited User accountHow to quickly and temporarily give your non-admin account administrator privileges, without having to log out.http://blogs.msdn.com/aaron_margosis/archive/2004/07/24/193721.aspx PrivBar -- An IE/Explorer toolbar to show current privilege levelA toolbar for Explorer and Internet Explorer that shows you broadly at what privilege level that particular instance is runninghttp://blogs.msdn.com/aaron_margosis/archive/2004/07/24/195350.aspx
The easiest way to run as non-adminThis is the really important one for your non-techie friends and relatives ...http://blogs.msdn.com/aaron_margosis/archive/2004/06/17/158806.aspx
"RunAs" basic (and intermediate) topicsA whole lot of detail about how to use "RunAs" to run programs under a different account.http://blogs.msdn.com/aaron_margosis/archive/2004/06/23/163229.aspx
RunAs with ExplorerHow to get Windows Explorer to work with RunAs (and why you might want to).http://blogs.msdn.com/aaron_margosis/archive/2004/07/07/175488.aspx
MakeMeAdmin -- temporary admin for your Limited User accountHow to quickly and temporarily give your non-admin account administrator privileges, without having to log out.http://blogs.msdn.com/aaron_margosis/archive/2004/07/24/193721.aspx
PrivBar -- An IE/Explorer toolbar to show current privilege levelA toolbar for Explorer and Internet Explorer that shows you broadly at what privilege level that particular instance is runninghttp://blogs.msdn.com/aaron_margosis/archive/2004/07/24/195350.aspx