I am 20 weeks now with my first child and just started to show a little bit.  I don't have any maternity jeans and I wasn't too interested in purchasing any unless it was very much necessary.  Recently while at work, I was getting extremely uncomfortable because my regular pants were digging into my stomach when I sat down and it was overall just a bad feeling for 8 hours a day. I started wearing these belly bands and it makes all the difference.  I am much more comfortable now.  I'm not sure if they'll last me through my whole pregnancy, or if I'm going to have to break down and buy maternity pants.  However, it is great for this weird in-between phase and I highly recommend these to others.

If you're unsure of size, I looked at the sizing chart and bought my pre-pregnancy size, which was a size 6 (size 2 in the band).  I was worried it would not fit but it did just perfectly.