The best way to get an Idea of if Lightroom is for you or not, is to download the
30 day free trial and give it a go. If you like it, you can buy a copy from where evers doing the cheapest deal (it most likely WON'T be adobe directly!) and use the registration number on the pack to turn the trial into a full version. If you don't like it, you've lost nothing but a little time and a chunk of disk space for a month :shrug:
Personally, I think it's a great program, I find it useful for keeping track of my back-catalogue of shots, the tagging helps me pick out all the shots taken on (say) a particular camera or film type, as well as being my first filter when it comes to PP. It's good for colour balancing etc, you can get the first shot correct, then copy the settings to all the shots taken in that light on that session in one hit - it may not be perfect, but it generally gets you 95% there, and leaves small individual tweaks that take a few seconds, rather than a few minutes per shot. This mounts up over 200-300 images
For me, it doesn't actually replace Photoshop, but it means I can keep Photoshop for the more awkward stuff, and the general day-to-day process is simplified and speeded up. Probably nothing I couldn't do in Bridge and CS5 with a few actions, but for the money, it's great value.