Okay, I'll post more info tomorrow.
FEATURES (these apply to Viconia as well)
INSTRUCTIONS-You can instruct Saerileth to follow you in casual or armed gear. You may tell her to wait, stand guard, or go into stealth mode from here also. Saerileth will carry a torch or put out the torch depending on your demands. If you ask her to sleep, she will do so provided there is a bed in the room that is owned by you.
COMBAT-Saerileth will do what ever it takes. She'll use melee weapons, ranged weapons and cast spells. She's very versatile. You’ll also find that she has a stealth mode which prevents her from bursting out into battle while you sneak. Realize that Saerileth is not a tank. She won’t do your job for you.
GUIDANCE-Player can show Saerileth her home and where it is safe to hang out.
INVENTORY-This feature allows you to share items, dress Saerileth, and arm her.
FLIRT-You can flirt with Saerileth and her response will ride on how close your relationship is.
Saerileth’s (and Viconia's) ROMANCE QUEST-Saerileth comes with a romance quest, similar to the romance quests in Baldur’s Gate II. The romance is time based, i.e. so much time must go by until she is ready to talk to you again. This preserves the original the quest progressed in BG2. I won’t give away how long between conversations but the wait is not as nearly as long as it was in BG2. It is important to note that she will initiate dialog with you instead of the other way around. You may be in a shop; you may be in a dungeon about to sneak up on a Troll. It mixes things up a little bit. If you respond nicely to her you will advance to the next stage. If you react badly you will not and the stage will be repeated after so much time goes by. If you are patient enough with her you will win her heart and the flirts will kick in with good responses (it’s worth it). The conversations will continue well after you have won her over.
OTHER FEATURES-
-Saerileth will sit when you sit provided there is a chair in sight.
-Saerileth will sneak when you sneak.
-Saerileth will attack who you attack, provided the target is not a friend. She doesn’t like stepping in between friends.
-Saerileth has set of target shock spells.
-Saerileth has a set of cloak spells which she’ll use depending on the situation.
-Summon Saerileth from anywhere no matter where you are. (This includes Shivering Isles)
-Saerileth has a summonable horse named Sillara and will ride Sillara when you ride your horse.
-Saerileth has her own voice set completely unique to anything in Oblivion, so expect to be entertained.
OBSE EXCLUSIVE FEATURES-
-Saerileth will repair and recharge her equipment daily.
-Saerileth is capable of learning NPC friendly spells through guidance.