Generally yes. particularly if all are not owned by the same person. When researching whether to get a non-.com name, I go to whois.sc and do a lookup. If com/net/and sometimes org are taken, I'll ususally take the info if it fits the extension. If com/net/org/info are taken, I'll often take the .us. I'd only take the .biz if it could be used as a business site.
Next, I'll look at who owns them and if any are actually developed, permanantly parked, for sale, or in use. These things are important to adding value in this priority list with 1 adding most value:
1. All other TLD's taken.
2. Extension fits the name.
3. One or more domains developed to a real site.
4. Domain forwarded to a real site.
5. One or more domains permanantly parked by one of the big holders who generally don't sell them.
6. One or more domains owned by the likes fo buydomains.com
7. Domains parked by a major player on a PPC or for sale site like afternic/sedo
8. Domain Parked anywhere.
9. Domain parked at a registrar
10. Domain taken, but unparked with error page.