We implemented 2 pretty large sites using the Multisite Enterprise license and it's been an absolute nightmare to be honest. First of all, their multisite isn't really so. Both of the sites are housed under the same web application, so when you make a backend change or module change that requires a restart, both websites get reset and there is an incredibly annoying system initialization that takes both sites down for 30 seconds to a minute while this happens. This makes continuous integration incredibly tricky.
It seems everytime we go to use some of the built in Sitefinity "features" they are always broken. Ecommerce was completely not finished and barely does anything out of the box. I had to spend a couple months of development customizing to make it work properly for our needs.
It's constantly giving vague and ambiguous errors that Telerik is aware of, but hasn't fixed yet. We tried using the Salesforce connector module, it stopped working after a few syncs so we had to go custom. We've been utilzing their Site Sync feature, it sometimes works, sometimes doesn't.
Getting it to play nicely with SSL and Load Balancer is also a huge chore.
We are currently having to restructure how the functionality is housed due to how Sitefinity is., I personally cannot wait to never use this product again.
Ecommerce, Lead Management, Brand information, Campaigns etc. The sitefinity forms have worked well for us without much customization, which is rare.