But they haven't had much public scrutiny yet, and the patent status of some of them is unclear. Buy from a reputable firm that understands security. There are lots of little things to get right, like making sure a copy of the key doesn't get written out to the swap area. As with any security system, that depends on who your enemies are. If your main concern is eavesdropping on the public Internet or at your recipient's site, you may be able to disregard some of these precautions.
Certificates are a way of assessing the authenticity of a public key.
In other words, they only matter if get the key from a dubious source, such as a public key server or directory. If you do use certificates, make sure you trust the issuer. I'm loathe to recommend specific products. In general, though, smaller is better. That tends to suggest that browser-based solutions are not ideal.