I've bookmarked this. If it's all well and good, then this could possibly be the easiest way for me to buy them. 
I'm building a bigger reserve and limiting my clients at 7BTC per day TOTAL (for all clients which they are ok with). It has to be limited because of traffic. If purchases exceed the limit that day requests get pushed to the next day. Soon it will go up to 10 BTC a day total increasing the flow.With www.SERVE.com, you fund your personal AMEX(proper establishment) account (3 days or less) then send me the $$$. In 4 - 5 days I will have your BTC with an invoice sent directly to you, here recently it has taken up to 6 days because of the transition from popmoney to serve.
It's good to see you are scaling up, but have you thought about taking MoneyGram? That way I can just wire the money to you from an envelope of cash I take to WalMart, like BitInstant lets me. That's really the killer feature that you have to beat. If you had that I might be interested.
DeathAndTaxes is right about it being very helpful for a broker to have a healthy amount of the Assets they are trading on hand. If nothing else it helps to make sure that you aren't going to have to honor a purchase price that ends up being well under the market price you have to pay for the bitcoins. You made a sweet looking website, see if someone will sell you some BTC for web or graphic design services. Any bitcoin you can gather for yourself can help to insulate you from price spikes. You probably want to start saving some of your dollars you are collecting in fees as well so you can take advantage of any downturns to add to your reserves.