Yeah, exactly same reasoning as Scott and Soondifferent for me. Part of what disappointed me my first time through PoE was how easy every encounter was except 2 or 3 (Adra dragon, Raedric's keep final fight the first time you get to it, and IIRC some big ogre clusterfuck which I don't remember well other than it being annoying). On hard-expert it's not like every single encounter is a struggle, but I've had a few fights I had to reload and be more generous with the spell and ability uses (Captain of the guard fight in Raedric's keep actually caught me with my pants down). It also limits your camping supplies to 2 and thus discourages rest spamming which I normally try to avoid doing anyway.
It also amplifies one of the aspects of PoE that annoys me, which is in their attempt to have better enemy AI they'll make a mad dash for casters/squishy backliners a bit more, and even with two fighters in the front and one of the fighters being able to "Engage" 4 targets at once, you still usually end up with enemies just walking past and beating up your wizard. Infinity Engine AI is dumber but you can somewhat more reliably hold enemies back from your squishy party members.
And another minor annoyance (Specifically with expert this time) is you can more easily eyeball AoE spells in Infinity Engine since they're always static, but AoEs are determined by stats in PoE. So once you start to get a handle on blind-firing burning hands you put a +2 INT hat on your wizard and/or one of those "Rings of overwatch" or whatever and then burn the hell out of Eder next encounter. Overall still liking expert better but that is one thing that's been a smidge annoying. Can also avoid it myself by not giving area-boosting stuff to damage dealing casters.