I haven't before found a typeface with a rounded look that I enjoyed, That changed today when I discovered Bariol. It's very readable and its rounded quality does not detract from its gravitas – unlike for example Helvetica which I think looks too playful. I could easily see Bariol replacing Segoe UI for my presentations.
Also Bariol is very affordable. You can get Bariol Regular for free simply by tweeting or posting about it on Facebook. The Light, Thin, and Bold variants are avalable individually or at a package and you an pay as little as €1 for each or €3 for the entire package. For the record, I paid €20 for the package.