Hm, I used to run through the revolutionary and then moskowski etude in f major for warmup, but I still like to do some scales/arpeggios. warming up with pieces may get your fingers moving, but things like basic scales/arpeggios are SOOOO nice when learning new pieces, because they're used! For example one of my friends is learning Moonlight #3? He has to look at every note in those upwards runs -to me, they're just separated chords! etc. you get those patterns ingrained. my piano teacher told me a story: when she was young she never practice d-flat melodic, and she has a piece she was playing when she realized it was just d-flat melodic! but since she never practiced it, it was harder for her, than, say, d harmonic. So it's really important to get those basics in early. Also, if you're bored with so called "warm-up exercises"... try to do them as fast as possible. faster and faster, and repeat long enough so that your arms ache, then learn to relax so they don't anymore -this would build stamina in a way that playing hard pieces wouldn't (since those pieces... well, most, aren't constantly using the same muscles, and they end when they end, and you're probably thinking more about hitting the notes than your arm)
so... warm up exercises are not just to warm up for that day of practice, but are important basics? ^^ to sum it up