My last company had a yearly requirement to do a "full" DR test. Luckily we had our own offsite DR location so we could do unofficial testing. We also replicated our drives and did our tape backups off the replicated drives. So we had to mount them up every Friday, but didn't attach the databases.
So I could get the databases attached and ready to go in about two hours. (Other non-DBA IT staff took about 4-6 hours off my checklist.)
As far as applications --the hardest one was actually MS's Great Plains to get going. We had to reset every test user's password by hand.
And luckily my managers understood the HA/DR difference. Our primary site were sets of two node clusters where we could do it.
The ability scale out, or spread load are a possibility with a few of these features.
My question is still how to scale out SQL. It never seemed that MS designed the system for multiple access to a DB. So while you can scale up the web servers or number of clients, you are restricted by the controlling instance. I admit I've been out of touch with mainline general production support as I have been supporting my companies SW product which doesn't do well with advanced SQL options.
A little bit of this and a little byte of that can cause bloatware.