Having played through the vanilla game several times, I decided to start trying mods. All in all, I have loved them. Isra has been fantastic, and Lava's mods have really added a lot of flavor to the game. (I really wanted more places to visit) It has been a really fun play through so far. From the fun perspective, I have zero regrets - these mods have been amazing.
However, I realized that everyone but Imoen had advanced REALLY far when we got to the Underdark. My PC conjurer hit level 19 shortly after they arrived, Mazzy and Isra were getting their HLA's about that time as well, and Jaheira and Aerie had long ago gotten access to all 7 cleric/druid spell levels. Immy is about 2 levels behind, but even she's hitting pretty hard.
Which made the Underdark fairly easy. Admittedly, I could have toned it down a bit - I love using Planetars and Devas - but so far there hasn't been a single "hard" fight. Deirex got a lucky shot the first time and killed Imoen, and I didn't have easy access to resurrection, but the second time he went down with barely a struggle. (I have tried to avoid reloads, but I wasn't sure if I could find a cleric to raise her in Ust Natha)
The upside is that not caring about XP means I can RP situations the way I would prefer. The fish in Ust Natha, for example. I usually take his quest for the XP. This time I told him to stuff it and walked away. I also chose to go full stealth on the scrambled eggs quest - even if I did have to waste three potions of invisibility in the process.
Perhaps it's time to up the difficulty...