It is still possible, but yea eveyone is right. For arbitrage between exchanges it can be difficult.
Why not do some tests with a small ammount of altcoin and try to do crypto-crypto arbitrage, learning by doing is the best.
Do not forget to add the exchange fees and withdraw fees charged by the exchanges.
Alt coins are better for starters, because for the most part, you don't have to wait very long for transfers.
you crazy?

I saw bittrex is awaiting 20 confirmations for a deposit of latium
while you deposit bitcoin in the matter of seconds..
Alt coins can get attacked, to prevent this, exchanges wait for more confirmations. Exchanges usually wait for 6 confirmations, so you cannot deposit bitcoin in the matter of seconds.
usually 3
latium deposits I had to wait almost an hour

some altcoins are faster than other, some exchanges need more confirmations that others.
BTC-E needs 100 confirmations for Terracoin

Litecoin is pertty fast in general, so is primecoin
daaamn, how long does it take to deposit?

Even though Cryptsy said 3, for some reason, I had to wait for 6 confirmations. Merchants, especially exchanges would want to be extra safe when handling trades. Terracoin's time per block is 2 minutes, takes 200minutes to fully confirm. AFAIK, terracoin was attacked once and I think exchanges would want to be extra caution about dealing with coins like that.
I understand that but it's ruining the trade..
how can you do arbitrage with 3 hour waiting deposit time
but yeah, I get why they have to do it..
guess you can keep some coins inside so you can trade anytime..