Two improvements that I would not minding seeing are:
1) Rock solid reliability. Since I signed up on the 29th September, I think there have been 3 days when the system has been down. I can't say whether this is representative of how its been all along, but I would say that with such a system, Safaricom need to ensure that there is virtually zero system downtime. This is because when it comes to accessing money, one needs to have absolute confidence that they will always be able to access their money whenever they need to. For example, if I load up my account when travelling upcountry in order to avoid having to carry a large sum of money around, I need to be totally sure that when I need to pay for fuel or accomodation etc, I will be able to access the money.
2) Secondly, I would love to see the banking sector embrace this service. I think that this service presents a great opportunity for mainstream banks to bring services closer to their customers. Imagine if you could deposit money into your bank account via M-Pesa...or make a withdrawals the same way. That would not only reduce the number of customers needing to go into banks, but I think that it would also mean that customers are able to pass more funds through their accounts. The 'unbanked' would also be able to operate accounts even where they are not located near branches. This could theoretically mean more savings, more people able to borrow (because the banks see their cashflows) and more businesses growing and expanding...therefore higher earnings for banks.
I have to admit I don't even know whether banking regulations etc would allow such services or whether there are plans already in the pipeline but I think companies in all sectors (not just banks) reallly need to assess how these and other innovations can benefit their businesses.