Sorry, but I`ve been to many Dillon forums, and the few people that have had "issues" with the primer system, have being people new to reloading, and where they have been too anxious to get setup....
Don't be sorry...like I said...some people have great success, some people have issues with the 550's primer system, AND Dillon helps!!!!....Personally I think its a great reloader that can be improved, apparently so does Dillon and they designed the 650.
The 550 has pumped out a gazillion rounds of ammo and it has an army of defenders if anyone even hints at critical comment which I think is a little insane. Heh its a reloading machine, I'm not in this sport to get passionate about a reloading machine....now diss my Colt 1911 SCG and we will be havin words

Note there are more 550s then anything else out there so you get a lopsided impression of any issues with the 550, i.e. more people more reports.
Its interesting doing a google on "dillon 550 primer feed problem", because you really get a perspective of all the different problems with all the machines out there. They all pretty much have occurences of problems with feeding primers but I think from the comments Dillon is the best at resolving the issue, and probably the best overall machine to be honest.
I really don't think you can go wrong with either of the LNL, the 550 or the 650 or the crown jewel the 1050.
My recommendation stands though, buy the features you want. If you want autoindexing, case feeder, and a 5th die...or if you maybe have a little arthiritis or even if you just don't feel like learning all the little tricks to getting fast with the 550 (read the posts), than a 550 maybe isn't the machine for you.
Oh yeah, one last thing, search you tube videos, people love to post videos of themselves running these machines. You can really get a idea of how well these machines run from the videos.
Cheers