This is actually a fairly complicated question. If you look through the release notes you will see that what we have here are different IOS Releases for Maintenance Fixes,New Features, LWAPP Recovery/Upgrade Images, different IOS's for 32Mb and 16Mb 1100 series platforms etc. etc :(
That being said, upgrades that flow along the same train like 12.3.8-JEA to 12.3.8-JEA2 will be safe and supported.
Here is the 1100 Series IOS Release Page and some examples of the different IOS Releases that I was trying to highlight above;
Cisco IOS Release 12.3(11)JX provides support for the lightweight access point protocol (LWAPP) for 1100, 1130, 1200, 1230, 1240, and 1300 series access points. When you use the Autonomous to Lightweight Mode upgrade tool to upgrade one of these access points to this release, the access point communicates with a Cisco wireless LAN controller and receives a full LWAPP configuration and software image from the controller. This release also functions as a recovery image if the access point fails to receive a full image from the controller.
Cisco IOS Release 12.3(8)JEB1 is a general maintenance release that concentrates on bug fixes and includes minor features. You can install Cisco IOS Release 12.3(8)JEB1 on any Cisco Aironet access 1100, 1210, or 1230 series access point.
Cisco IOS Release 12.3(11)JA1 supports autonomous 32 Mb platforms. 16 Mb platforms and platforms supported by Cisco IOS Release 12.3(8)JA and earlier (350, 1100, 1130, 1200, and 1230 series access points and 1300 series access point/bridge) are supported by Cisco IOS Release 12.3(8)JEA1.