The decision to purchase an ESP is an individual one. Know some who have never used it, others who used it a lot.
Have had 3 of these. All 3 bikes MINIMUM Race Tuner, breather, non HD pipes. Not one issue regarding a denial for mods, but others have from what I read.
#1 On the 02 RK did a little better than break even. Bought 3 extra years for total of 5.
#2 On my 07 SEULTRA which also had SE cams, high comp pistons I used it too many times to count. Was about $1500 ahead on it when I traded it for my 10. Got a refund on the ESP of $1200 since had a few years left.
#3 On my 2010 SEULTRA got the 5+ years. Am about $300 ahead with 3 years left on it. Recently had lifters, front wheel bearings, and a rotor replaced. Cost was $50 for all, except upgraded to SE lifters (paid difference only on parts) since stock are crap.
One reason I buy the ESP is that there are so many internal crap parts - like the compensator - plus the well documented electrical glitches on an Ultra - figure since I ride a fair number of miles odds are in my favor to break even or better. A lot of folks think a CVO motor has SE (better) internals but they do not.
I do not buy ext. warrantys or service contracts on anything else - only HD. If you only plan to ride a few miles, probably no reason to get one. If you ride a lot, maybe. For me the odds are way better than blackjack, historically.