Taking a long weekend to Savannah in early February. Thinking of taking a day trip to HH. Any suggestions on what there is to do there in a single day? Is Harbourtown worth a visit?

Harbourtown has a private marina, a lighthouse, a few “trinket” and clothing shops and a couple of bars/restaurants. It’s not really a “destination” but rather someplace you might stop at for lunch and maybe browse the shops if you happen to be in the area. It certainly isn’t worth going to Hilton Head just to see Harbourtown.

the real draw of Hilton Head are its beach and golf courses.

Nothing and no.
You get more of accommodations for your money in HH, and Savannah is only a 45 minute drive, so that is where we usually stay.
Nighttime walks on the beach are nice in HH, if you know your constellations.
Blufton is kind of cute.

There is a toll to enter the "private community" (HH is full of them) where Harbourtown is located, You should take your parking pass if you want take a walk out of bounds of the "private community" and re-enter, (as we were sternly informed by the gate keeper at the sidewalk check point).

HH is so stupid that it is amusing.

Peerfect last remark!!!
Visit something else--Beaufort, Dafuskie Island.

It's touristy as heck, but what they hey, I was a tourist visiting HH twice, once with my husband and once solo and while the island had many good restaurants, I really liked Salty Dog Cafe, the shrimp toast was to die for, sooooo rich I could only eat half of it. The fish bites were pretty good as well.