You can read all the details on IE10 here:
If terms like HTML5 and CSS3 just hurt your head, here's a good summary of what to expect with IE10 over IE9:
Microsoft will be pushing out the update to IE10 over the next several weeks. However, you can update to IE10 in Windows 7 right now if you download and install it manually:
32-bit and 64-bit non-English versions can be downloaded here.
Not sure which link to use? See How To Tell if You Have Windows 7 64-bit or 32-bit for help.
There's little reason not to update. I just updated this morning on my main Windows 7 computer and had no issues whatsoever. I did need to restart my computer after the installation.
Important: You should install any recommended updates in Windows Update before updating to IE10. Even thought you're probably upgrading via one of the manual download links above, the Windows Update system is still used. Previous uninstalled updates or a broken Windows Update system could cause problems when updating to IE10.