CS5.1 has issues with brush characteristics. Comparing CS5 on my laptop to CS5.1 in my desktop, using the same tablet and mouse with identical brush settings. There is definitely some lost control issues as far as softness goes, and control in the middle of extreme brush pressures. I can better explain the problem with a example file I made if I can email it somewhere to adobe or whomever. This may seem slight, but as a retoucher using PS daily, this is a complete pain and time is money.