I have little experience with brick and mortar video blackjack, but two things to look out for:
1) Deck may reshuffle on every hand. This means you can't count it.
2) Sometimes the payouts blow on overblown slots with a blackjack mode. If blackjack pays 2 for 1, (instead of 3 to 2) that's really only an even-money payoff, and that alone yields a big house edge.
Also, I've heard of some video blackjack machines that are even more slotlike, in that they don't use a real deck of cards, but are constructed to have, say, a 95% payout, like a slot.