The secret url link which saves your bitcoin is never a good idea. First you can easily lose it and second, its very easy for a hacker to look at your cache and try to access it without your permission.
It was a smart move for the SatoshiDice guys to move into a user/password authentication system, I was never confident investing in the site with that link - Not sure how the guys with hunderds of BTC on the bankroll slept at night. Will be even better when they have 2FA enabled as well.
They're working on 2fa implementation, the sooner they get it done the better. almost every sites have them, i don't know why satoshidice still doesn't have it. it'll make users feel more confident when investing.