V-Flyer

Do Upper Class passengers get access to the Delta One lounge in Boston?

Yes, Upper Class pax can use any of the Delta one lounges. From the Delta website:

Admittance
The Delta One Lounge is available to

Same-day departing or arriving Delta One ticketed passengers (i.e., seated in the Delta One class of service);
Delta 360'™ Members departing or arriving on a same-day ticket in Delta First Class;

Same-day departing or connecting flights operated by the following Delta partners in their respective first and business class cabins specified below:

Air France La Premiere;
Air France Business Class* (Long-Haul);
LATAM Premium Business Class;
KLM Business Class*;
Korean Air First Class and Prestige Class; and
Virgin Atlantic Upper Class

Thanks! Looks like it offers seated dining rather than the Sky club!