People have been saying this since launch day. I put in a reservation at Best Buy the day after launch. Over the next week, plenty of people were taunting in the Best Buy threads that none of us with reservations would ever get them, or that Apple would obviously fill all its online orders before shipping any more iPads to other stores. Instead, I got my iPad a week after launch - and then got a call 3 weeks later that my iPad was in, because my name apparently didn't get crossed off the list! So by the time the people who ordered online when I put my reservation in got theirs, my BB had gotten at least two shipments of my particular model in. I was also watching Target inventories in my area, since I could cancel my BB reservation if I bought one elsewhere.
Ordering online is a great way to guarantee that you'll get one - eventually. It's low-stress, low-effort, but it will take time and you know that it will take time (although 1-2 weeks is significantly better than the 4-5 week wait after launch). If, however, you're impatient and have some time to invest, watching the store inventories and checking regularly could get you one sooner. It's a bit of a gamble, though. So basically you've got guaranteed in 3 weeks, versus possibly today - it just depends on which one sounds better to you.
