First of all, one should gamble only the money he/she affords to lose.
Then, your argument about investment and Bitcoin rise is invalid, since he/she can just simply buy some more Bitcoin to cover the loss if it's the case.
No. Bitcoin gambling is not more safe or more unsafe than any other gambling. People have to be careful to not get too greedy if they won or not get addicted (especially if they've lost).
The only real problems are: play at a trusted gambling site, else you may have surprises (delayed or no payout in case of win) and, if you "think" in fiat money, the Bitcoin price fluctuations can "affect" (up or down) the money that stays for longer periods of time at the casino.