I have been using Instawallet since I first got into Bitcoins. People who tell you not to use it honestly just want to wow you with their knowledge of bitcoins. Sure, its probably not the safest place to save coins, but so long as you aren't keeping thousands of dollars in any accounts there you are fine. I initially liked it because of its ease of use. Also, it works on my phone. If you really want to be safe though (And I've found keep yourself from spending your coins), print your own paper wallet at printcoins.com-its easy.