We have just installed 2 Fas250's to provide backed exchange storage in the Uk and Germany and also to provide file serving on those 2 sites.
Both are using Iscsi for the Exchange database and logs Drives, it works very well and replicates the data to its conterpart, so in the event of a failure the data is on the remote site ready to go.
Replication is async, and they have some good exchange intergration to make sure the exchange data base is valid after snapshoting it.
To recover a 32GB database to a backup that was 3 hours old took less than 15 mins.
Its so good we are in the process of buying some more for our US sites. Very cost effective and is an established product, unlike EMC's Iscsi box which is their 3rd attempt.
I would try and find a reseller that know what they are doing though, some don't seem that great.
Cheers
Matt