Experience with DeepDyve group plan?
I've no experience with DeepDyve specifically, but there are a few things that stand out as issues from a quick look -

a) Coverage. They seem fairly broad, but it would be worth double-checking they include, say, the top-fifty most used journals by your researchers. (It's a little fiddly to produce such a list, but quite an interesting thing to have available.)

b) Access rights. In my experience, people get quite frustrated by read-online-only access models with no print/save capability, and this seems to be the DeepDyve approach. Downloading is apparently an additional cost (the plan gives you "20% off" without saying how much the basic price is)

c) Accessibility/usability. Requiring users to go to a specific service to read the paper (rather than the websites they're used to) will cause friction and probably a bit of confusion.

None of these are insurmountable, but they're all things that are worth considering. On the plus side, their basic prices seem competitive to standard document-delivery services, assuming some kind of a bulk-purchase discount, and access seems to be immediate rather than delayed.