Sure Hubble's pictures are prettier, but there's a lot of cool science coming out of the nifty MESSENGER spacecraft. She's up for a third Mercury fly-by in two weeks. She'll go into orbit in 2011 and she's the first spacecraft there for 30 years!
Already we've seen her video leaving Earth on a 2005 fly-by. Her first two Mercury fly-bys showed part of the planet we had never seen, and also answered some questions about the Caloris basin (and its formation), the planet's exosphere, and the planet's magnetic field.
Go visit the website to hear more or read from the special issue of Science from May 1, 2009.
Here's a picture from her last fly-by: