id ask a few more questions
1 is this to be used fulltime for commuting or just when the weather is nice
if full time you might want something with a little widertire tread than say a brompton to handle rain and even snow a little better
2 do you have ANY intentions of using public transport as a backup if so a folder might be of interest a brompton in this case would be perfect as those can fit between your legs and the seat infront
3 do you have other forms of transport? i know you say you'll only go 3 miles buti thought id be the same too but with no other transport I go everywhere so some cargo capacity might be of interest
4 whats the storage situation like at home? do you have a shed garage or utility area where this bike can live or would something compact be of value so it could live in the hallway or under the stairs
5 what kinda weight your looking for? do you have to carry it up a lot of stairs?
6 whilst at work where will you be storing it if a private carpacrk no big issue but if your only option is street parking I might suggest going ultra small once againbrompton so it can come inside with you and be stwoed out the way in your place of work