Just to re-iterate what other reviews have said, the collect DOES come with BOTH DJ hero games in full retail packaging and shrink wrapped for extra freshness! Haven't had a chance to play it much but I am loving what i've played so far. The DJ deck also comes with batteries so you're ready to go straight out of the box. DJ Hero 1 is also compatible with a PS3 Guitar Hero guitar, and DJ Hero 2 is compatible with a microphone.
Another note, this is a little more than a casual music game. Meaning that there is a learning curve and some time should be spent with tutorials. Easy mode is extremely easy, so if you want to enjoy the mixes in levels, it's advised to stick to any difficulty higher than this.