Well, I'm with you. I was sitting on the fence, twiddling my editing fingers and pinching my pennies, delaying the inevitable. Part of the reason for my upgrade sluggishness was the complete absence of a flashy, sequin-bedazzled, must-have upgrade features in Lightroom 4. LR4 sports no automated 'make-this-into-a-Peter-Lik-$1million-print' filter, no horizon-line hugging grad filter updates - just tweaking and fiddling.
Fortunately, my hand was forced by the need to upgrade in order to process RAW files from my new Nikon D800e. It was fortunate, because Photoshop Lightroom 4 is a very solid (and affordable) upgrade and it transpires that version 4 does have a killer feature in it's newly spandangulated Shadows slider.
The replacement of Lightroom 3's 'Fill Light' slider with the 'Shadows' slider is the most noticeable 'Great Leap Forward' in Lightroom 4. Big FD I hear you say - a name change. Well, along with the moniker transplant the white coats and mohawk guys did some serious upgrading to Lightroom's shadow engines. The Shadows slider does incredible things to even the deepest shadow areas of a file and even better - it breathes new life into old files.
Adobe Photoshop Lightroom 4 | Shadows Recovery User Review
Feel free to ask any questions in the comments section over at the review - I answer all sane queries - and even the wonderfully insane ones.
Cheers - Todd