I went through the same thing (encoded everything in itunes, the found out about LAME).
First off, let me say that in audio, your ears are king. If iTunes 192K sounds good enough to your ears on your system, then don't let anybody tell you different.
That being said... in my experience LAME blows iTunes out of the water. iTunes has problems with skips and pops on some tracks, LAME does not. iTunes also tends to brighten up the high and low end, which may sound good on lower end sound systems, but doesn't represent real fidelity. For testing LAME, I suggest using "--r3mix" without the quotes as your encoding options. For more hard numbers and facts, check out
r3mix.net.
On another note, why wouldn't you want to use VBR? It let's you use more bits where they're needed, and spare them where they are not. Over all if done properly, VBR results in both better sounding and smaller files (I will refrain from commenting as to whether iTune does it properly...)
Re-encoding isn't all that bad...
(Thankfully, I was able to create a ripping farm of NetBSD boxes at work... made short work of 800 CDs).
Hope this helps...
-(another) alex.