Just going to toss in my $1.50 w/inflation :-)
1) integration with accounting packages such as Quicken
Define an API, but don't specifically choose an accounting package. Deal with what the "use cases" are, rather than what Quicken expects. Quicken is nothing like what most companies use, with a full double-entry ledger system
Accounting packages are just wierd. How companies use them are even wierder. Getting a compnay (or their accoutants) to change accounting systems (le alone learn any new software) is a lesson in futilalty. Probally the best thing you can do is provide ways to export data, and pray. In other words this shouldn't be made a priority, although it would be a nice sell.
Ahhhboy, I've got to remember to spell check these things before I e-mail them out. I mean it's one thing for everybody to think I'm an idiot, but another thing entirely to write your IQ on your business card, sheeesh!