Pretty good, All forums so far, Ebay, Youtube all work well. Flash movies play well but only upto flash 7. SWF games run, but many are too slow, some are great though (Bowman is my fav) Most Sites load surprisingly quickly - about half speed of a firefox page. Very occasionally on some sites there are some text alignment problems. You can zoom into web pages for ease of reading too.
The extra cost for the Web, Mpeg2 and QT plugins is a scam though... Factor this in before purchase.
Media filetype support is superb. mp3 xvid divx mpeg4 avi wmv vob all play very well. The screen is bright and super detailed - I was expecting eyestrain,
but have watched full movies comfortably.
Music playback is good, but I think smaller devices are better suited to that.
Photo viewing is superb. drag screen to move between pictures Zoom rotate and flip.
I went mad and bought the DVR dock. (£50 from Currys if you haggle) This allows the 605 output to be displyed on your TV. Also it turns the 605 into a hard disk recorder. Recorded films or shows can even be edited on the device to crop adverts or overruns.
The best feature is the way the 605 networks with your PC and allows wifi streaming of your PC media library content.
Needless to say, I love this device....