From what I have experienced, IE9 RC is a solid improvement over IE9 beta which was quite good too. And looks like I am not alone. On these new releases, IE has reversed the trend of falling market share and have now 0.78% gain across all operating systems.

IE9 Reaches 36 Million Downloads; Internet Explorer Share Grows

Since its release on February 10^th, the IE9 RC has already been downloaded over 11 million times. Together with the IE9 Beta, IE9 has been downloaded over 36 million times since its initial availability on September 15, 2010. As of February, IE9 has now surpassed total combined downloads of IE8 Beta and IE8 RC, and Net Applications reports that IE9 now represents 0.66% of all worldwide browser usage share on Windows with 2.09% usage share on Windows 7.

Net Applications also reported this month that Internet Explorer share increased by 0.86% across Windows. Across all operating systems, IE share also grew 0.78%.