I'm sure that once you got deep into, you'd probably find banking software pretty difficult. Since it has to work. All the time. 100%. No compromises. That sounds pretty hard.
Perhaps depressingly, much banking software doesn't work 100% of the time. Or at all, occasionally. I've worked on a few large financial apps, and the general quality level of the industry is pretty disturbing. They aren't architected much better than a good consumer webapp - more buzzwords, more heavyweight process, but the actual quality of the code isn't any better, nor is the developer's understanding of what they're doing.
I've noticed the same problem from a consumer's POV too. I was just on IM with a friend last night whose online banking account just stopped working for her. I can't log in online with my BankNorth account, and I get some weird error code whenever I try a "forget my password" or "reset my PIN". My dad notices that a couple cents disappear from his bank balance every month, and no matter how much he checks his arithmetic, there's no way to make it balance. Several people he's talked to have noticed the same thing.
I've heard that the industry used to be better, that people actually took "100% uptime" and "don't lose money" seriously before Java and Y2K and all these newfangled development practices. I knew a developer that was an early employee and later VP at Stratus, and she really did know her stuff. But she seems to be a dying breed - everything now is moving towards J2EE and outsourcing where nobody really takes responsibility for the quality of the software anymore.
Sometimes I think that all the top-notch engineers at Google and Facebook should quit their jobs and start financial software companies instead. Because they really are more highly skilled than the folks who build the software that manages your life-savings. Facebook manages 3 TB of data in memcached alone without a hitch - that's more than we have on disk at the financial software company I work for.
Hm. Well, my Bank of America account has been flaky and they redesigned it in some terrible way recently. But I imagine convincing a bank to use your software is probably harder than getting your code adopted by the mobile handset carriers.
