I have multiple TLDs for some of my domains, but not for my personal or "hobby" sites. For anything where I want to point related TLDs at different servers, I'll buy multiple "versions" of the domain - usually .com and .net, and very occasionally .org.
For my "business" domains, I'll buy the .com and .net, then use the .com as the primary site and the .net as either the support or the backup site (or, in one case, the staff site). One domain has the front-facing site using one TLD, another TLD is used as Linux nameservers, and a third TLD used as the Windows nameservers.
One of my domains has the top three TLDs displaying the same content. I bought all three TLDs to make sure someone else didn't set up a similar site on the .net or .org. I've only got one domain set up like that, though.
I only own the .com for my personal site, and for one other "hobby" site of mine.