I continue to use aluminum bolts with my Tenpoint Stealth. I found a end of season clearance on them 10+ years ago at a big box store and picked up a half dozen. Got to the cash register and they scanned WAY LESS than what was marked on the shelf. Went back and bought every last one they had. I believe I have about a dozen left from that purchase. Once they run out I will switch to carbon.
When I bought my Tenpoint Turbo XLT II last fall I went to carbon off the bat with it.
i know compound bow users are told to constantly check their carbon shafts for cracks and other damage. the real hazard here is shooting a damaged arrow and having it "explode" upon release which can send parts of the shaft all over the place. especially your face and hand, google images and look at this.
so, wouldnt it be the same for crossbows, i know i wouldnt want one "exploding" that close to my face.
The thing with carbon crossbow projectiles is that those suckers are *stout*. They are built as such to compensate for the increased torque exerted by a crossbow, hence why it ain't a good idea to throw a regular compound bow-rated arrow on the rail and send it. Odds are good that the regular compound arrow would blow out, even if you found a way to get it to nock (not likely). I use the Parker Red Hot carbons and they have never shown a hint of cracking. Regardless, one they go through a deer, they get tossed, but as far as routine target practice into a block, while I still inspect them before use, cracking has never been an issue.
At the end of the day, use whatever floats your boat. As long as it's rater for the poundage/other specifications on your particular crossbow, it's all good, be it aluminum or carbon.