When it first came out nobody bothered with it really because there was barely anything to do. Just imprimaturs and sight seeing as there was no waypoints anywhere (those quests are now missable!) Later on when Delve was introduced it was the best thing ever, challenging and it got the community all worked up trying to come up with strategies and such. It was good times around then.
Despite the lack of content and the overall feeling of rushed/incomplete the expansion was hinting at every corner, I have very nice memories of those first months.
People getting back together (FFXIV was on break before the release of ARR), finally new zones, new areas, new jobs, new stuff to do. Lots of new mechanics, lots of new stuff to ease players' woes (warping around through waypoints etc).
It was fun doing those Colonization Reives at start, they were hard back then, challenging, took time to clear and mobs were actually hitting a lot and evading a lot when you didn't have ilevel gear.
Overall the atmosphere was really nice.
It got even better when Delve got released shortly after, it was really challenging and it proved to be content for all sort of people.
For random noobs who joined NQ mobs runs to slowly farm Plasm, other groups killing mobs outside, and serious LS trying to do the real content.
It made Linkshell communities come back, they resurrected, suddenly people wanted to apply to shells instead of doing everything lowmen or with 2000 mules.
For me? One of the best periods in FFXI's life. Despite how they *** it up with the scaling or with the fact that full runs were giving WAY MORE PLASM than they ever should've, I think Delve is probably one of the better thought content SE ever released for FFXI.
Quality, variation, challenge, drops, loot system, currency... simply fantastic.
Things kinda started going downwards sometimes after the release of Delve2, imho.