I have a Barska 3-9 tactical (shorter tube) scope on an M&P 15-22 and it is not bright, somewhat cloudy at higher powers and the lighted reticle lights up the whole inside of the tube. It's a nice looking scope for an AR type rifle but performance isn't too good. I have had much better results with Centerpoint scopes in that price range.
However, if you're going to use it much look into the Nikon Buckmaster line for very good glass for a reasonable price. Moving up from there, the Nikon Monarch series and the Bushnell Elites are great.
The new Redfield scopes are a good value, too.
My recommendation for an AR is the Leupold Mark AR, which has a ballistic drop knob and glass that makes picking out bullet holes at 100 yards a snap. I have the 3-9x40 model with mildot, which is about $350. Without mildot is about $300. A good scope makes target shooting so much more enjoyable, so save up if you can.