I am using Photoshop CS5 Extended (English language) on Windows XP SP2 32-bit (currently in trial mode but will acquire a serial number soon). CPU is AMD Athlon 64 X2 Dual-Core 6000+, RAM is 3 GB (4 GB installed), Graphics card is ATI Radeon HD 2600 Pro.
For me, the speed of Camera Raw's user interface clearly has improved over ACR 6.0 but still is significantly slower than ACR 5.7 used to be.
Two bugs I found when trying ACR 6.1.
The first bug was already there in previous ACR versions; I don't know then it was originally introduced. It's about the focal length range display in the panel right beneath the histogram. There, the aperture, the shutter speed, the ISO setting, and the focal length of the current image are displayed and, in the case of zoom lenses, also the range of focal lengths. And the latter is wrong for third-party lenses. Obviously ACR tries to derive the focal length range from the lens ID which however only works reliably when camera and lens are of the same origin (Canon lenses on Canon bodies, Nikon lenses on Nikon bodies, Minolta or Sony lenses on Sony bodies etc). For third-party lenses, in particular those of the Sigma brand, it does not work.
So please stop to try deriving the lens specs from the lens ID! Instead, try reading the lens data from the lens info tag in the XMP metadata first (aux:LensInfo; see namespace "http://ns.adobe.com/exif/1.0/aux/")! Only when the lens info tag is missing then you may fall back to deriving the missing data from the lens ID.
The second bug is about the drop-down lists for selecting a lens profile in the Lens Correction tab. When the Camera Raw window is extending right up to the screen's rightmost edge and when the profile names are longish (as they usually are) then the drop-down lists will partly be outside the screen area! So it will be impossible to read the profile names and to access the drop-down list's vertical scroll bar; you have to resize the Camera Raw window first in order to make room to the right.
So please adjust the position of the drop-down lists so they will always be displayed on the screen entirely!
Thank you for pointing these out.
For #1: hopefully this will be taken care of long-term by the EXIF 2.3 spec with its new tags.
For #2: this is a known issue on Windows and I hope to have it addressed by the final version.