My two bits
I have used various PC based software programs and hardware over the years. One year ago, I made the switch to Mac (MacbookPro) and I bought the Apogee Duet. I had no plan to use Logic Pro 9 (the Apple audio recording program), but have actually found it great (after quite a bit of getting used to it from using Ableton previously). I have not yet had a single crash, error, loss of material, sluggishness, problems with audio quality or anything!! Coming from a PC world, this has been such a nice change!
I hear what people are saying about starting off with cheaper interfaces than the Apogee Duet. However, if you are using a Mac (you MUST use Mac with the Duet), trust me, Apogee is the way to go. I checked Craigslist in my area and you can get a used Duet from around $300 something. It's worth it. Obviously, if you have the cash, the Duet 2 will be better as the new features listed by others are an improvement. But the Duet 1 is also just fine.