I have grabbed 1st growth futures on multiple occasions over the last 15 years. Should be no problem if you deal with a reputable firm or a local store you know and trust.
Remember you are giving your money away for something you won't see for a couple of years. If the wine store or online provider you give your money to goes out of business you are screwed. That said, I have never had a problem. It's a great way to get some outstanding wines at around half the price when they are released. My favorite buy was the 5 first growth cases I bought on future for the 1995 vintage. Average future price was 100.00 / bottle. Kept 6 of each, sold six of each for 5 times what I spent.