First of all

to CF hope you enjoy your stay and find it as useful as many others have.

To the Mods/Admin team that run CF. Now to your questions.
Ive had Broadband from NTL for nearly 3yrs now and I've had an engineer out only once. Ive had no problems setting DD up or anything. I guess I must be one of the fortunate ones.
The only way you will find out for yourself is wait until its installed and use the service.
Hope this help in calming your nerves