Upvote:1
The question is a little vague, since "Heaven according to mainstream Christianity" is vague, but there are some differences we can infer.
- The Terrestrial Kingdom will not only be Christians. The Terrestrial Kingdom contains "they who are honorable men of the earth, who were blinded by the craftiness of men". This presumably would contain those of other religions, and even those who do not believe in God but lived honorably. According to most Christian denominations, you need to be Christian to go to Heaven. There may also be additional requirements, such as be baptized, or being a member of the correct church.
- There will be faithful Christians who do not go to the Terrestrial Kingdom. In particular, those who go to the Celestial Kingdom will not be in the Terrestrial Kingdom. So, if you are in the Terrestrial Kingdom, you will not be in the same place as Peter, or Moses, for example. So you may be bummed out by that. On the other hand, in mainstream Christianity, all faithful Christians (or Jews before Christ came) will end up in the same place. (Although, you could say that those in the Celestial Kingdom would not go to the heaven according to traditional Christianity, having accepted "Mormonism". The Celestial Kingdom is quite different from where traditional Christians think Mormons would go, though.)
Upvote:2
I want the answers to focus on the day-to-day living/quality of life/level of perfection in heaven.
That's next to impossible, as there aren't any detailed (canon) claims of day-to-day activity, quality of life, etc. that could help us out here.
"What is heaven like?" is one of the great mysteries. It probably has a similar answer to "What is being alive like?": you'd have to be there to know.
Comparison is even more tricky.
"Christians say that they will be happy by 1 unit." "Mormons say citizens of the Terrestrial kingdom will be happy by 2 units." "3 units." "4 units!" "Infinity!" "Infinity + 1!"
Ostensibly, yes they are quite alike. There are many similarities as you pointed out.
Probably the biggest difference between mainstream Christian heaven and the LDS terrestial kingdom is this: mainstreams Christrians in heaven are as happy as they could ever possibly be. Those in the LDS Terrestrial kingdom aren't.