is Nextbook a good tablet brand?

I don't have direct experience with them, but all the same, I'd stay away from them. They may be cheap, but you get what you pay for. Looks like they come with Ice Cream Sandwich (Android 4.0), and with off-brand devices like these, you shouldn't expect any significant updates. Sounds like a slow processor, too. There are much higher quality budget tablets available like the Hisense Sero 7 Pro and the Asus MeMO Pad 7 HD--granted, they cost up to twice that of the Nextbooks, but you'll get a much better experience (as well as better support).
 
After having purchased such a tablet at WalMart (Nextbook 8 inch HDMI) and am posting to confirm that there is no OS update - ROM's basically don't exist for it, you have to do a lot of searching internet to find out how to root it with minimal success, and therefore, my opinion is that it is a glorified leaPad2, w/ Google play preloaded, minimal bloatware, hdmi access that may work, that does not look like it has any room for or intention of progressing, as of yet. Good for kids to play w/ somewhat. :-\