I have a Diesel Apex.
I did rout the exhaust out under the van, so the van does not smell at all. There is an issue of smell though, if the engine works and the wind shifts towards the house, you do smell some diesel fumes. You would too if it was regular gas, however the smell is less obnoxious.
Can't compare to a gas slide in (never had one) but they do shake a bit.
I would assume that one reason they do not use a diesel may be the cost of the engine (that's what Les told me a while ago), as they are more expensive. Supposedly though they will last much longer.
Heat not much of an issue as it gets plenty hot (never been a heat freak, so take this with a grain of fat free salt.)