Do the enemies level up to accomodate, or are they the same?

You don't take your levels with you. Just money and Persona database I believe.

This changes things significantly...thanks!

ChrisTaran posted this in another thread. :)

1. Social stats. (i.e. courage, intelligence)
2. Persona Compendium. (every persona you've collected with their levels in tact)
3. Persona Compendium discounts.
4. Persona slots (You will start with 12)
5. Max social link items (for fusing ultimate Personae)
6. Money. (so sell any unneeded items before the game ends)
7. Play time.

You're welcome. :)

does that mean that my yukiko will have her updated persona?

No but the Persona you get to fuse from Maxing her social link will carry over.

You're forgettinging soemthing or perhaps never did something.

Do the personae in your compendium keep their acquired powers so I can just breeze through Margaret's s-link, or do they do what they did in P3 and delete the acquired skills?

They are kept. You can max Margaret out as soon as you can afford to.

Thank GOD, I got an especially bad ass Surt that I wasn't thrilled to give up so easily.

Their strengths and weaknesses change.

For example Yukiko becomes null to fire but stays weak to ice
Chie on the other hand becomes null to both ice  and fire.

Just a tip for those playing through again: Before finishing the first time, be sure to get a persona with the ability that halves the HP consumption for physical skills. This makes levels 1-40 incredibly easy, as you expend very little sp, and do lots of damage.

There are many things that can change in the second playthrough....
 
1. at the start of the game, you will acquire Moon Tsukubame 5 of them, It Restores HP and SP fully to the party and revives all dead player, cannot be used unless main character is dead......
2. There are more chances that DEATH will appear.
3 You will gain more EXP and Gain more money in battles....
4. You can fuse the Ultimate Persona, Izanagi-No-Okami level,91 world arcana specializes in Element Fire
5.The second bosses in Completed dungeon will be a lot more easier to defeat
6.Money and Play time you had in your last game will be the same in your second playthrough
I suggest you fuse the Personas Mada, Sraosa and others that are lvl 81 so that you can buy it on the compendium
7. Quests that can be done will increase
9. Hama and Mudo instant kills will not always hit
And lastly........... Discounts In the Shirokyu Store was it Shirokyu? anyway discounts will increase during rainy days

Oh, maybe i got the wrong things..... Did not know about that......