I have X5 and X4 on my laptop right now and have not experienced any issues. (Both 32 Bit) I loaded X5 when it first came out and used it several times while trying to learn the new features but over time I found myself using X4 more. I also have Adobe CS4 and CS5 on my Desktop and have not had any issues. I prefer using Photoshop CS4 but I am fine with CS5 for the other Adobe products.