the whole market of flash carts has evolved very quickly.
by the way there are much cheaper flash carts than the r4 that offer the same features, don't waste your money. to earn more about all the different flash carts check out gbatemp.net
haha when I first started using flash carts, I had to use the 2 slot method, which means that you had a ds cart in the top slot that allowed you to run homebrew off of a gba cart that you had stuck in the bottom one. it was a complicated system that wasn't the greatest.
that being said, my ds is dead now. I'm thinking about getting a psp as right now the 1st gen refurbished psps are really cheap