The rust around the heater mounts is just surface staining. You don't have to worry about it going through the tank. KA used the Tri-Dura porcelain and underneath the white layer is a dark blue that is actually much more durable; sort of like the old Maytag tubs where the white layer of porcelain would rub off in the area opposide the high fins on the Gyrator, but the dark blue porcelain underneath lasted and lasted.
Greg, I should have been clearer. It does heat the water to around 180, but it does not heat the dishes to much more than 155-165 in the lower rack. It's plenty hot to deform cheap plastic in the top rack, but my Rubbermaid 1 quart sippy bottles have survived years of washing in the lower rack. I was very pleasantly surprised that they also survive the dry cycle in the Kenmore with just the heating element under the bottom rack. The first couple of times I used it, I only left the dry heat on for a few minutes then pushed the Power Miser button. As they kept coming out OK, I kept increasing the length of time the heating element was on until I found that they survive the whole heated dry cycle.
For the water temperatures, I have one of those instant read thermometers and I bleed the hot water lines before each fill up to the main wash with the 18 to make sure that the water is at least 140F. I'm usually washing something or cleaning the counters or stove so I make use of the water. The pipes are insulated. If nothing else, I run the water into a container and use it for other things so it's not wasted.
I was amazed at the heat loss in the hot water standing in the pipes in houses in Florida where the pipes go through the concrete slab. Unless the hot water line is purged before each fill, the dishwasher fills with only mildly warm water and in some cases, that's with those special plastic pipes.
Since the Kenmore Ultra Wash has the high temp wash option, I sometimes start it with only warm water if I have items in it with starchy food soils. Then I bleed the water line until it's 140F for the main wash and let it heat. It adds a good bit of time to the cycle to heat the wash as it scrubs along, but it sure cleans well.
Yesterday, in John's shop, I saw an older TOL Maytag with ss tub and door with the integrated controls and that big handle that swoops out in an arc. The tank had a leak that Jason fixed and the frame is whacked, but if the customer who sent it in is in any mood to get rid of it, I will take the door and buy a ss tub Maytag and use that door on it. It still has the Quick Wash cycle which has mostly disappeared on the models I see in the stores. Somehow I think I will eventually get my hands on a machine like that if not that one.