Why can't MPEx be ... is easier to use?
It is deliberately not easy and also has the 30BTC registration fee in order to put off all but serious, tech-savvy investors. They're not geared to dealing with high volumes of newby questions.
However, if its S.DICE shares in particular you want there are a number of 'passthru' trading sites. I use
Havelock myself which is a subsidury of a Canadian bricks & mortar business, the proprietor of which, James (username lightbox) to be very helpful and responsive to suggestions for change.
I will warn you at the moment there is over 7% difference in price buying via Havelock but that's likely to be because there was substantial trading and price movement in S.DICE the end of the week (mainly on MPEx but with knock-on effects on the 'passthrus' too) so I guess it'll take a little while for things to 'settle'.
Edit: 4.7% difference in ask price now between Havelock and MPEx - I guess some trader was reading my post