Depends on the type of riding you'll be doing. I bought a Scott Aspect 45 which is an entry level 'serious' cross country bike. It cost about $750 on sale - and yes the brakes came with it as standard. It's for off road cycling and I also have road bike.
If you're cycling on roads and gentle off-road (park) trails - or commuting to school then what you've got is fine. It's likely to get stolen so cheap is good.
If you are going to be hammering down a steep singletrack with roots and rocks then it will fall apart and maybe kill you.
A more expensive bike is stiffer, lighter, tougher and the controls work better - the shifters change gear in difficult conditions, the brakes have more power and control, the fork has good travel with rebound control and maybe a lockout etc.
The thing to do is to try one. You need to go to a good bike shop and see if they'll let you ride one - but be prepared for sticker shock. I bought mine off eBay - but I knew what I wanted, can understand the specs and can assemble it
