If you get 1 thing right in your application, make it the User Interface
The thinking goes like this... To be really successful, a great strategy is to do a smaller number of things, but do them noticeably better than the next guy. In other words, don't spread yourself too thin. Nobody ever became fabulously successful by doing a long list of things in a mediocre way. If you want to get noticed, you've got to do something worthy of notice, something that most other people stop short of doing (because it's too hard, or takes too much investment for them to do). You need to take something to the next level. That's what gets you noticed and gets people talking. That buzz creates momentum and can bring all sorts of good things (reputation included) your way.
If you want to do something really well, a good place to start is figuring out what "well" means. By what factors will your task be measured? And exactly who will do the measuring? Knowing what buttons you need to push, and who owns those buttons is a tremendous advantage. It helps you plan your game - how you're going to go get that high score in the right people's eyes. It's worth a few minutes, days even, to make these things explicit. Think about them. Write them down. Once you've got a handle on those things, choices about how you're going to spend your time, what pieces of the overall puzzle you're going to invest your energy in become a lot easier to make. You can make wiser decisions. For example, the Dot-com bust taught a bunch of people that there's no point in investing heavily in getting "clicks" or "eyeballs" if you're ultimately going to be measured only by actual sales. Oops, a bunch of people were measuring themselves on the wrong scale.
Now to apply this to software products... What buttons do you need to push to make a software product successful? When you hear high-flying CEO's being asked about what made their companies successful, I've never heard, "Well we have 47 features and the competition only has 40, so we're more value for the money." Rather, you'll hear things like, "We're the ones who made it really simple to do X." Making a software product simple is all about the User Interface.
In software, who's going to score the product? Not your boss. Maybe not even the person that "purchased" the software (on behalf of an organization full of end-users), but the actual end-users themselves. They are the ones that are going to love or hate your product and determine the level of repeat business and referrals you get - or don't get.
That being the case, it's a shame that most User Interface work is tacked onto the end of a project like a necessary evil. (And we all know that things left to the end of a software project are the first ones to get cut.) Seems to me that people have it backwards. Do the most important things first. Make them absolutely shine before you spend your time doing anything else. Because if you haven't got those things right, nothing else matters. If that means you had to cut some features, but shipped the features you did finish in a product with a User Interface that is really strong, you'll be far better off - in the eyes of the people who matter most: the people holding those buttons you've got to push - the users.
I don't know a single software company or team that wants to deliver a piece of software to their customer and never get repeat business. What that means is that the end-goal isn't just getting the contract signed off or getting paid "this time". It's about creating fans of your work, so that they keep coming back and actually refer their colleagues to you.
The importance of User Interface investment is sometimes a controversial topic. I've seen people argue very passionately on both sides. I'm a gear-head by trade. I came up through the ranks of development organizations and am certainly not a graphic designer. But I'm often the minority in the development organization when it comes to my strong beliefs in putting User Interface first. Developers pride themselves on not being influenced by shiny, glitzy User Interface baubles. But baubles are not what I'm talking about, of course.
If the scale your success is going to be measured on, is how often you get repeat business, and referrals - how many fans of your work you create; and the people doing the scoring are your users, then it's clear that User Interface design has to be your priority. Nothing is worth doing if it isn't worth doing well.
Here's a bit of irony: I'm currently developing a software product aimed specifically at development teams (Devshop.com). These are the very folks who claim to be immune to the hypnotic effects of a great User Interface, and argue regularly that it's not important, compared to all of the very technically challenging things (and interesting things to them) that happen on the back-end. I've demo'd the tool to close to 50 of these people in the last 6 months. More often than not, one of the first things out of their mouth is, "Wow. That UI is incredible." Their eyes light up when they say it too. It's like a little spark of desire was created inside them. Now I know that as long as my feature set is comparable to others in my category, they will desire mine more than the other guy's, because I took the time to do one thing better than the next guy: focused on User Interface design, to make my end-user's experience actually desirable. I put the user first, brochure second.