No
"Is it a good proposition to take even money with blackjack with a dealer A up?"
Not if you're not counting.
"Some casino's [casinos] offer it,"
ALL casinos offer it; it's insurance!
"but don't advertise it,"
Not true. In big letters, on the felt, it says, "Insurance pays 2 to 1."
"which would make me think that it's good for the player. Thoughts?"
See above. Bad bet, unless you're counting.
Don