Hi,
Just to put my two pence in, we have just been through a similar process of evaluating which SAN to purchase, we have around 8 Hyper V hosts all with local storage and really wanted a large amount of storage (when does it stop growing!) and some redundancy in terms of Hyper V hosts - we looked at Dell, HP and then came across (through edugeek of course!) Nimble.
HP fell through pretty quickly based on the timeframe to just get a quote from them. Dell was a very close second and we liked the idea of single vendor but didn't want to be held back by that idea (we also purchased 2 x R620's with 256GB RAM in each for a new Hyper V cluster, along with 2 x Dell 6248 switches to be dedicated to the SAN switching - the R620s are extremely power efficient compared to our old PE2900's and even the R710's - not to mention going from 5U to 1U!), I had some very good conversations with Matt from Nimble (with plenty of questions from me) and ultimately we chose them, I think the key for us was to look very closely at what was actually being offered by each vendor in terms of performance in real terms as well as accessing future growth and needs (possible VDI etc.), for us there was a clear winner!
We went with a single CS240 (unfortunately our budget wouldn't allow for 2!), which means that we will leverage snapshots for short term backups but will keep DPM and some very large NAS boxes and tape library going for long term/disaster recovery). We haven't received it yet, so will try to update how we get on when it arrives, but really looking forward to putting it through it paces and checking out infosight.
I'm in Devon, but if anyone wants to see it in action (when we've got it in and running of course) or have a chat feel free to PM me.