update november 2010: it is reported in the comments that the next release will support these controllers. However, which controllers are supported is not clear. Also, we may have to wait for quite some time before squeeze will be released.
Just a quick note: it seems that the new Dell RAID controllers are not supported by the current stable version of Debian: Lenny. The S300, H200 and H700 controllers as supplied with the R310, R410 and 'higher' systems, are thus not a great choice if you want to keep things 'stock'. You may have to run backported kernels and installer images and I couldn't figure out if these controllers actually work with these latest images.
The Perc 6/i controller is supported by Debian. It seems that it can only be supplied with the R410 and higher systems. If you have any additional information, like actual experience with these controllers, please report this.
I installed VMware ESX 4.1 and installed DEbian Lenny om top of that without problems.
Please note that the network cards of the R410 are still not supported and will cause a headache!