HI Kenny,
1. Spokes 2.8 is just a bug fix issue and it should be completely backward compatible.
2. You are right that Spokes 2.7 and 2.8 cannot coexist on the same machine. The 2.8 installer will automatically uninstall 2.7 first.
3. You don't need to explicitly uninstall 2.7. The 2.8 installer will do that for you.
4. There is no change in the registery settings.
2.8 is the last version release for 2.x. If you are not experiencing any issue with 2.7, I do not see any particular advantage to upgrade to 2.8. The next Spokes release will be 3.0 with a lot more features and that will NOT be backward compatible to 2.x.
Wei