I switch to a hard drive system back in early 2000 and have never looked back. Having your music easily accessible, but more importantly having it organized in multiple ways via playlists is a tremendous boon to listening to your entire collection. And to Tvad's concern, you can organize playlisst via albums so that you can play the entire CD as originally recorded.
My primary concern has been software upgrades. I use Apple's iTunes on a Mac hardware platform. Since 2000 Apple went from OS9 to Jaguar and now Tiger as major system software upgrades and now they are switching to Intel chips for another system software change. I should also mention that within each system software version there were numerous upgrades such as 10.2.4 to 10.2.6 to contend with. Additionally, every few months there is a new revised version of iTunes. The problem is that every software upgrade has the potential of really screwing up your system. I've never been seriously burned, but you have to be very careful and do a good deal of research before implementing what seems like even minor software upgrade. And if you don't upgrade, eventually Apple will stop supporting your software version, which while not terminal, has it's own set of serious problems.
My solution to all this is to keep two separate computer systems. One system is the master version and the other is slaved. The slave system is always one software revision behind the master. For instance, right now the master is using Jaguar 10.3.4 and iTunes 4.7.1 while the slave is using 10.2.8 and 4.01. You just have to deal with the fact that computers suck!
Enough about the bad stuff. It's a phenomenal way to listen to music. I would strongly recommend you utilize all the features of iTunes, or its equivalent, database. Give a star rating to each song. That way you can sort by how much you like each song and eliminate ever listening to the "dogs" of you collection. Tag each song by genre, release date, purchase date, composer and label. The more info you add, the greater your ability to organize playlist.
QUESTION: I still keep the original CD after I've ripped it. Do you keep your CDs?