Hi James
I started with the ST80 and Orion SSAG because a lot of other people were doing the same, its like the defacto starter kit, but I did upgrade the guide scope rings. Guiding using PHD.
Then I added an additional 60mm scope to the rig for widefield so ditched the ST80 because of weight and balance issues and was switching the guide camera and imaging DSLR between the 2 scopes depending on what I was doing. This worked fine but was a faff when changing imaging scopes.
Have now got an adapter to connect the guide camera to the standard finderscope that came with the ED100. This combination guides very effectively for my relatively short focal lengths. Basically I can get away without OAG with my rig, flexure is not a problem for me and the guiding results I am getting are fine at this level.
When I grow up I will upgrade to something different but that will be part of a bigger upgrade and its not crucial for me right now as I don't seem to not have any guiding issues.
The main reason for wanting to change will be to help eliminate flexure.
I have never yet had an issue with the Orion SSAG not finding a guide star by the way and I am in a light polluted burb of Sydney with a very bright night sky. Just remember to take a dark in PHD which makes a huge difference.
Ultimately, had I known what I know now when I started this hobby ,with the rig I have, I would have gone the finder guider route right from the start. Its a lot cheaper and removes a lot of weight and balance issues when piggy backing. But part of the fun of this pastime is trying different things out and learning whats good for you.
I have not tried EQMOD pulse guiding or anything else like that but am sure someone else will pipe up on that subject.
cheers