P5 works well in some areas, not well in others. The improvements over P4 made it worth the money to me, but some advertised parts still aren't acceptable. Check the P5 Beta forum for bugs. CL has said they hope to release SR3 this month or early next month if things go well. I'd wait for the SR3 release before shelling out any money. Don't delete P4 from your system. Install P5 in a new directory. How to link to the old P4 libraries from P5 is explained in previous posts. I use Vue and Tailor, and neither one works well with P5 output. Vue intends to support P5, but there's no update yet for that. Tailor doesn't recognize P5 .cr2 files, so I have to go back into P4 whenever I make a new .cr2 and want to use it in Tailor.