Microsoft is advising Vista beta testers to burn their downloaded ISOs as slowly as 1X or 2X to avoid corrupted media.

It says three quarters of failed Vista installations are due to dodgy DVD-Rs.

Of course, the really interesting thing here is not that Vista installations are failing due to recording problems, but that for the first time, we have some widescale data on the problem of lack of optical media reliability.

APC Magazine

we have some widescale data on the problem of lack of optical media reliability

Which is somewhat flawed.  (Microsoft's information)

DVD-R media is not the only issue when burning...as was not the case when burning issues creeped up on individuals and CD-R media.  It is also the hardware involved.

Low-end DVD burners have second rate technology..with specification tolerances at substandard values.  These can be difficult to recognize because 99% of those helping you with burning issues will first tell you to purchase top of the line media.  It's not a bad suggestion, but when the new media also fails to produce a quality disk...well, that leaves only one item left.  This also counts out firmware upgrades due to the simple fact that firmware has no effect on a low quality laser LED.

So, when burning anything there are simple steps to follow:

1.  Burn at medium to low (but not 1x) speeds for DVDs.  2.4/4x to 8x maximum even on 16x or faster drives.  (nothing at this time is faster than 16x, but there will be)
2.  Don't use OverBurn technology or options.  (burning an 8x disk at 16x speeds and cramming more data on the disk then specified)
3.  Burn no faster than 16x when burning music CDs.
4.  Burn no faster than 12x when burning CD ISOs to CD, or when creating backups of operating system CDs.
5.  Use reputable media.  Memorex has made decent leaps forward in quality...however Verbatim, though more expensive...is worth it for higher quality movie backups.