Rich--are you talking about from the downloading perspective? If that's the case, I'd like to know about it ...
Yup - In my own experience, both Dropbox and Hightail suffer from this; clients send large files over those services and sometimes they're fine, but sometimes achingly slow; like I said, Wetransfer seems totally solid, as does AWS. This is all just my experience, but it seems repeatable enough that I dread getting large deliveries over those services.
How pertinent; just received another delivery today via Dropbox; folder of audio files, ok, download the whole mess as a single zip - zip is corrupt! OK, download one at a time; Dropbox takes 15minutes to download 100MB of data! OTOH, Wetransfer Plus and AWS S3 totally solid and fast as always... This is purely anecdotal, but seems like more than a coincidence that I only ever run into these issues with Dropbox (and Hightail) deliveries - sometimes fine, but sometimes really slow and glitchy.