DragonForce - Through the Fire and Flames, Guitar Hero Smash Hits/Greatest Hits stem set has the keys and backing/rhythm guitar in one stem. I immediately could tell that the backing guitar was played by someone other than Herman Li or Sam Totman.

The rhythm guitar stem from the Guitar Hero III stem set is completely different, and when I actually look at the DLC chart for RS 2014 (took bloody long enough), I observed that lead and rhythm guitar were charted in RS2014 as it was in GHIII.

When looking at the RB3 DLC stem set, I noticed that Keys is the chorus in the background for the majority of the song, but there are no separated vocals stems. Also, the guitar stem is lead and backing/rhythm combined, and sounds terrible by itself.

The drum stems from both Smash Hits and RB3 sets have odd echoes from other stems, but RB3's stem set is the worse of the two, with the vocals leaking in at points (kinda have to be listening for that because it isn't obvious but it is there).

In many songs with censored lyrics (due to the ESRB being a bunch of wussies or because of laaaaaaame copyright garbage or both), listening to the vocals stems often leads to hearing the censored lyrics either at a very low and next to inaudible level, or only partially censored lyrics, but enough to satisfy the pundits of censorship (yeah, don't get me started on them).

The backing vocals for Snot - Deadfall (Guitar Hero: Warriors of Rock), are half-censored at best, but since the enunciation of the lyrics is rocket speed fast, that's no surprise. There are parts where one could re-add the censored lyrics (I did this already), and it doesn't sound too bad ('Well, vivé la f***ing France, man!' is all vocals so that is very easy).

There's likely a lot of things I've noticed, but what's really funny is that after hearing the stems, I can listen to the downmixed version and still hear the stems, if I focus on it....lol