How DOS programming is useful at these days? Does people still use it?

Yes there's still people who do not like bloatware and want to use older PC.
All these people must be using it.
http://www.computing.net/dos/wwwboard/wwwboard.html

The International Space Station used Dos
http://83.67.55.228/index.htm

The mars rover may of used part of dos .
http://forevergeek.com/news/nasa_dos_glitch_nearly_killed_mars_rover.php

Heres a good example of dos users, build your own supper computer
http://dosbeowulf.tripod.com/index.html

And there are people like me and bubach who are making 32bit pmode dos like OS.

I always liked programming for DOS, but Win NT/2000/XP killed DOS.
So I had to learn the Win32API. But I like how DOS gives more control over the PC.

You can still program like in dos and get good graphic, here a game in my os;
http://www.dex4u.com/images/guipong.PNG

Also you can run your programs in dos dosbox in xp
http://dosbox.sourceforge.net/news.php?show_news=1

Kewl! I'll have to try out this dosbox programs for some of the old dos arcade/console emulators I liked but can't use anymore.

i am using dosbox + enviroment for it called D-Fend and it works very fine (except some rare problems with mouse)

I think DosBox is a great peace of code, it works with all the old dos game i have tryed and its very easy to setup.
Also has my OS, can boot from Dos, it runs my OS fine, good for getting screenshots etc.