I stopped using RealPlayer when it became abundantly clear that I could expect it to:
a) Do annoying things such as callback home with unique ids
b) After objections to a) still do it but bury disable options in far flung places of the app where few people would find them
c) Run background processes all the time for no good reason
d) Nag me to buy the premium version
e) Lead me around a maze of links on the Real site just to find the free version when it needed an upgrade.
None of these things are true of VLC so I switched. Real had it's day in the sun and it blew it.
The other thing I remember Real for is the monumental cockup of RealDVD. Here is a product that stripped out DVD copy protection and replaced it with an even more intrusive proprietary DRM. Sadly for Real it didn't even get to be a commercial product because DVD stakeholders took offence to it DeCSSing DVDs. Maybe they should have cut the stakeholders in on a piece of the action.