Yes, absolutely. It's a lot cheaper than buying them from some guy riding on your coattails a couple of years later.

If 16 bucks decides the go/no go on something like that you are probably looking at a hobby project, not a business.

One way around this problem is to have a bunch of generic domains that you do your first trials on, if you find that something 'has legs' you can always decide at that point to come up with a good name and get a complete set of domains.

It also will help to stop phishers that will use the .net or .org version of your domain in a spam campaign to tell people that their password may have been compromised and other jokes like that.