I'm probably going to be investing in a vag-com this summer but need to try to keep costs down. I'm getting a brand new laptop in coming weeks and I thought it'd be a good addition to the laptop... but is the USB interface worth the $70 extra I think it costs? And would a Bentley manual be worth investing in?

However you can always buy a V2 cable (dual K line compatible) from www.obdtool.com for $80, then go to your local CompUSA and get a keyspan serial adapter for $50 (or online for less http://www.cdw.com/shop/products/default.asp?edc=323100)

Then you need to register VAG-COM for $100. So you're still looking at $230 but it's still less than the $270 it would cost for the whole thing from ross-tech directly. Also if you already have a serial port then you don't even have to worry about the usb to serial adapter. Note that ross-tech does not support USB to serial adapters so you'd be on your own. I bought the above adapter and it worked under linux for me just fine for regular serial connection (minicom serial terminal and a safety dongle at work) so I can assume it would work with VAG-COM as well.

And the Bentley also worth it. Ross-tech sells it for $70 for registered users of VAG-COM only and claims that he makes no money on those which I find hard to believe given that BimmerZone sells if for $66.40 + $5 shipping. http://www.bimmerzone.com/bentleymanualsmain.htm

Good luck!

I know the faster sampling rate is for data logging and not for error code pulling and soft. recodes, but the Bentley CD is money better spent IMHO.