I would recommend studying a bit for the ITE, simply because other residents and interns do study, and despite what some PD's say, my experience was it is used to evaluate you. I also am reasonably sure that intern year ITE exam scores were used to help select the chief residents @my program. HOWEVER, I was never asked, and am 99% sure that program did not supply, ITE scores to any fellowship program. The ITE also isn't supposed to be used to decide promotion. However, my experience was the PD told us not to study and then made a big deal of the score reports when he got my scores...actually I had an above average score but probably not above average for my residency program. My PD was trying to tell me I might have trouble with the boards but since I outscored 50% of other house staff even as an intern I was trying to figure out how that was true...I think he was just thinking he should threaten me b/c he felt like I must not be studying enough.
The USMLE will be more important in fellowship selection, since some programs may ask for your USMLE scores. they won't ask for ITE scores because they aren't allowed to. My experience with the ITE was that there was a lot more time pressure than on the actualy IM boards. The ITE was somewhat similar to the IM boards, but the difference was the board questions seems a little longer/more involved and a bit better written, and we had more time per question. I believe at the time I was taking the ITE, the medicine programs were allowed to give us a variable amount of time to take the exam...our program gave us less time than some other IM programs, and I did have trouble finishing the exam, particularly when I was an intern. My USMLE scores were also better than my IM ITE scores, perhaps because I studied a little more but also I think b/c medicine ITE is more based on memorization and USMLE is more general patient management stuff.
The best way to study for the ITE is to study with MKSAP. MedStudy would be another option, but I think MKSAP is a bit closer in format. If you just want to get a decent score, then doing MKSAP practice questions might be the most helpful, especially ifyou are time crunched. To study for actual boards it would be good to read Medstudy and/or MKSAP so that you actually learn/retain the stuff, but for sheer scoring purposes the questions may help more simply because they tend to be repeats/similar from year to year.