I fitted S&S 551 easy start cams to my 2008 FLSTN and my brother fitted easy start 583's to his 2008 FLSTF.
They've been in our bikes for maybe 13 months and we've had NO bad experiences with them.They work as advertised ;meaning that start-up is certainly less laboured and kinder to the starter and electrical system, and they sometimes make a click or clack kind of sound on shutdown(i think S & S mention that in one of their blurbs also)
I bought mine based on speaking to people here in Brisbane and also on the big,fat dyno chart on S & S's website.This dyno chart has since been altered and shows these cams to be somewhat weaker than previously described.(but still stronger than stock)The 583's are actually stronger-based on our comparison runs-and these are the ones that i would recommend for a Heritage.
Two things to consider:if you fit cams then you should also have already done a stage 1 upgrade,and secondly unless you remove the valve covers you'll need adjustable pushrods and probably new lifters and maybe even new valve springs(depending on mileage,the way you ride your bike and the lift of your new cam.)
So,do they work? Well,yes they do.The 583's have good low down through to upper mid-range grunt(with stage 1) and they certainly start easier.Another plus is that they come with better bearings included in the kit.Also remember that these are NOT new technology -compression release cams have been widely used in many different types of motors for years.
You could do worse than check out a series of posts by member "Sage Counsel" about 12 months ago regarding his,mine and others' experiences with these cams.