I've been trying the iphone to trade stocks and I agree with this assessment. The EDGE network is impossible to trade stocks. I wasn't able to trade anything on the EDGE network, as I had to run through the gauntlet of login screens and place the order, and in all attempts except one, I never was able to get through to the last order screen without having to re-enter my trading key and starting all over again.
The wi-fi was much better in terms of not having to re-enter the trading key again and again, but I noticed another problem...
in the transition from the first order screen, where you enter in buy/sell, symbol, shares, limit, etc., and the second one, where you confirm your order, the information wasn't exactly transferred, and as a result the order wasn't placed. I received the message "Buy/sell in order does not match strategy definition". I don't know if going back and forth between the first and second order screens until the right information is transferred, and then confirm it, will will fix the problem. I thought I noticed a "N/A" where there should have been a "buy" or "sell" statement on the second order screen, but I was at my day job and don't have time to record notes and stuff. I'm also wondering if adding the Tablet program from Inventive Labs, where the second order screen comes up in a new window in Safari, will fix the problem. I'm going to try this and then I'll post a follow-up, but I wanted to post my findings to see if anyone has found a work-around.