I'm just an engineer, not a pilot, but I always understood that the DC-9 lineage aircraft land a little hot (faster) than your typical 737 or A318/319/320 because of the reduced low airspeed lift. I would not be surprised if that results in a little more wear on the tires, brakes, etc..., and I know it's definitely a harder landing than a 737. So if you're on a 717 (fka MD-95) with AirTran, as well as the older MD-80 series run by Allegiant Air, expect it.

I think most people notice tire issues on the MD-80 and 717s because there are fewer and fewer carriers running them, while 737s and A318/319/320s are more common and parts available at almost every major airport. In the case of the 717s, the part commonality of the MD-95 design is very distinct from prior MD-80 and DC-9 designs. E.g., AirTran regularly has to fly tires in from ATL for 717s, although BWI and MKE are sub-hubs for AirTran and they may stock them there as well (I've seen some parts available at MCO too). That's just been my observation flying a lot of AirTran since 2003, and Allegiant for a couple of years, the parts availability probably increases visibility, not actual frequency (other than MD-80s being 15-20+ years old on average).

Again, I'm just an engineer, not a pilot, and I don't have extensive commercial airline equipment familiarity either. I am more of an enthusiast. I heard SWA will be retiring the AirTran 717 fleet (along with Business Class ... sigh), leaving Allegiant as one of the few MD-80 series operators, but it makes sense (SWA gets one of the newest 737 fleets via AirTran, Continental being the other operator of newest 737s fleets). I can't remember if US Air has retired its DC-9s, and I know American still has MD-80s as well. They are solid aircraft, if taken care of from what I've seen.

In any case, the Allegiant crews are definitely the most rested. The way the run their operations, focused on 8 hour days for their crews (virtually part-time), vacation/bundle-centric sales instead of airfare, really works very well, and very profitable too. And with the size of their MD-80 fleet now (I remember when it was barely a dozen), they have the aircraft to fly in, take out of service if required, etc... The cost model using alternative airports is extremely smart, although I thought the move to try to infiltrate AirTran at MCO instead of sticking with SFB was a move that wouldn't work out.

The one thing I will say is that I feel much safer on a 717 and MD-80 with regional carriers like AirTran, Allegiant and American, than 30-50 seat passenger "puddle jumpers." I also find it sad that Boeing ended the DC-9 lineage and 100 passenger aircraft, which allowed Embrier to come in with the EJ-190/195 and get customers like JetBlue and others in the regional game. It never became a strain on the 737's sales, but that's like because of how Boeing positioned it. I think AirTran showed they work, and work very well, for a regional carrier, but they were the only ones that bought in number (and wanted more).