I don't know if this is something mtGox already have been notified about ( I would think so), but the usual thing do to in the business world when somebody wants to buy something is to give the customer the service/good the customer wants, and then if there's fees, either add these to the base price, or have them included in the price, not giving the customer less than what he expects.
Say a customer wants to pay 2 BTC to someone, and he goes to his mtGox account and enters an order of n BTC to buy, then the 'Total to spend in USD' is immediately listed.
Unfortunately, the fee is deducted from the purchased BTC, so the amount of BTC is less than what he asked for, so he then has to do another purchase to top it up to get exactly 2 BTC, and unless you want to put up your calculator (and you have to know your fee percentage as well), it seems like you always have to buy more BTC than you need just to be sure when doing a purchase quickly.
So what I ask is that basically when purchasing 2 BTC, 5 BTC, 10 BTC or any other amount of BTC, this amount is what is available to the customer after the purchase. The fee should be removed from the fiat amount and not from the BTC amount imo.
I'm sure there's a lot of people trying to buy n BTC on mtGox which they intend to spend on something, and then quickly see they didn't get n BTC, but m BTC (n BTC - fee paid in BTC), thus they need to do another purchase to get the complete amount, and usually if they buy too much, then they may need to sell the excessive amount of BTC again (if they wish to have only mtGox USD on the account for instance), which means even more fees have to be paid.
So to fix this I think something like the following should be considered:
MtGox state that to have n BTC available to you after the purchase of BTC, m amount of fiat currency have to be paid, then mtGox could decide for themselves if they wanted to have the fee paid in BTC or in fiat money.
So, I'm pretty sure about somebody is going to answer this thread with:
1. Did you file a support ticket ?
2. Did you contact Mark on irc ?
So in short: No & No.
I just post it here in the hope that somebody at mtGox may pick it up and act on it. It's not a huge problem, but I'm sure many find it as a minor annoyance.