Mostly differences in behvaior between the regular gmail interface and the mobile interface. Mobile interface loads faster and is easier to display; it lacks some of the functionality of the full interface (no surprise), especially in handling attachments and following links embedded in emails. I find myself using the mobile interface if I just want to quickly check messages; I prefer the full interface if I expect to look at attachments.

One tip I suggest is to use the full interface as an easy way to deal with MS Office attachments - have gmail display them as HTML and you can usually get the gist of what someone sent to you without needing the "doesn't exist for us" msoffice viewer.