I've only played FFXI for a few months and got up to L40-something, so bare with me!

Hmm. It's very different and not at all, depending on the angle you're looking at.

The appearances of characters and locations are very similar - although a hundred times better looking, obviously enough.
The classes are very different, and the lack of an absolute healer class is... interesting to say the least. Party dynamics - although I've not got into a large party yet - must be very different to FFXI at the moment.
There are chocobos, airships, crafting still uses (shards and) crystals, the items are similar.

The layout of the map will be very familiar - three major starting cities and one 'capital' city of sorts. Various little locales dotted around here and there, although at the moment I don't believe there is a large amount to do in them... they're obviously going to be adding a lot of extra storyline though as the number of places you can go to is notable. There are roughly six "small towns" so far that I know about.

The core of any MMO is a glorified grind, which this game has, and a lot of people to grind with, which this game already has. Possibly not as many as it needs to become truly awesome, but it's got 2.1k on my server at the moment and that's certainly not terrible for a CE-only release to date. It'll be interesting come the 30th September.

It's too difficult to say on pacing at the moment. Let's face it, it's only been out for a few days and nobody will know how the pacing will be for the higher levels yet, nor will they know exactly how much SE will change over the next month as it tries to balance things out. The story pacing? Every 10 levels from what I've seen so far, which is pretty much how it worked in FFXI if I remember rightly.

This game has got so much room for additions though, and it's fairly obvious that SE will be introducing a lot. How that compares to FFXI in it's current state... well, we'll know in about 8 years, I guess. xD

Basically, the game bleeds FFXI to me, but also has some very, very notable differences that will make fairly big changes to how you play the game.