Go for Lightroom 2. It is designed specifically for a logical workflow when processing pics. it is very intuitive, IMO. I use it way more than CS3, although CS3 does have features not found in Lightroom 2.
I'm a PS fan, never used anything else though. I have a legal mac copy, infact i have 6 copies for my studio, luckily it aint coming out of my bank account LOL
I use it for creating artwork more so than post processing, so something like lightroom or aperture may be better for photo enthusiasts.
I've just got a new laptop with CS3 and Lightroom although I've never even heard of them
I use to be very good at design on photoshop about 4 years ago back in college, but kind of forgot about it once I entered the real world... Wanting to get back into it lately so I may be giving those tutorials a try. Mostly thanks to planted aquariums and finding photography again through it.