According to the GIMP.org website:
It's been a while since the last release. Quite a few bug-fixes have piled up in the stable branch, so here's another release in the stable GIMP 2.6 series.There are just a ton of bug fixes included in 2.6.9 for a wide variety of languages. The full details are at developer.gimp.org. Should you be concerned? Probably not. I haven't found GIMP 2.4.6 to be in such a condition that I've been dying for an upgrade. Also, the option to use synaptic (and thus apt-get) to perform such an upgrade on my Ubuntu 8.04 LTS (Hardy Heron) computer doesn't exist (no, I haven't gotten around to upgrading to Lynx, yet).
Even for the Lucid Lynx, you have to jump through a few minor hoops to install GIMP 2.6.9 and unless you really need the bug fixes listed, it's probably not going to change your GIMP experience appreciably if at all.
Not sure if I could make the 2.6.9 upgrade option available for my current version of Ubuntu or if I should care. I know I could download the 2.6.9 tarball and install that way, but I prefer to use apt-get/synaptic to manage my applications.
I checked and for Windows using the Windows installer, the latest version of GIMP available for immediate download is 2.6.8...close, but no cigar.
The interesting news is that 2.6.9 was released on June 23rd, making it the first release of any version of GIMP since last December. Looking forward to GIMP 2.7.0 in another six months.