If it's a computer that is just going to be used at home and be out of sight, no reason to worry about it at all. For all I care, it could be set up in a milk-crate.
But I take my computer with me for DJ gigs, and as such, I like it to have a small bit of "bling" as you call it, but only because lighting is part of being a DJ. That, and it can be fun for LAN parties to show off depending on who is there. Also, since I've been building since the early 90s, and that was the cool thing to do in the late 90s and early 00s, it's a holdover "old-school" thing for me. I do it for the same reason I own things like an NES, Genesis, etc, just a nostalgia thing.
http://www.last.fm/user/chasewolf J.O.B. Squad 4 life
No, it's not 2003 anymore. Windowed cases and flashy LEDs were cool when I was a teenager, but nowadays it just looks tacky. I even disconnect my HDD & Power LEDs because they were too bright and annoying.