I tried SRST Manager about six months ago and found it to be pretty unreliable. There isn't much documentation about what to do to prep your IOS devices for provisioning.
The provisioning worked on about 20% of our devices. TAC didn't know much more about getting it to work than we did.
In failover I think I remember having problems with DN translations, such as using 4-digit numbers to call 10-digit DN's. These can be fixed with the dialplan-pattern command, but we had to enter it manually iirc.
We also had trouble using TACACS with it. I have yet to find anybody who thinks using this is easier than coming up with a generic E-SRST config.