Hardware controller's like 3ware's should be able to improve read performance in RAID-1, and 3ware claims that it does. Even Intel claims that it also does load balancing:
http://www.intel.com/design/chipsets/matrixstorage_sb.htm
Also, due to drive load balancing, even systems with RAID 1 can take advantage of faster boot times and data reads. In the office there are more background tasks such as virus scans, data backup, e-mail, and data processing consuming storage resources. Implementing a basic RAID 1 configuration helps alleviate the bottleneck encountered by running these added tasks.
I find it very difficult however to find an evaluation of this on the internet.
The theory is sound but i there are no tests or testimonies. Perhaps it is difficult to benchmark or perhaps there is too little interest? I suppose people interested in performance generally look at other solutions.
I think this aspect of RAID-1 is too little known or understood (as many aspects of different RAID levels, judging from this forum) I suppose it is largely ignored because performance gain might be minimal on typical desktop systems.
I am interested in this because of the following system: it will serve as a home-gateway, providing broadband access to the entire house. It will also serve as a samba server, serving mostly a photo collection among other things and an itunes library. While photo access will be irregular, it will be streaming songs at least half of the day into the living room. And it will be a workstation. These will be virtual xen machines on the same box.
I plan to RAID-1 two 320gb Samsung SpinPoint F drives together. The entire house is dependant on this machine and a reinstall will take time, hence the redundancy. Also it is of course terribly cool to have raid.
If the load balancing works however, I think it could have a positive impact on performance. While it reads songs from one disk the workstation reads from the other.