They are helpful in the sense that they test your understanding of concepts...A LOT.
It is suggested that you use the 1001 only if you have weaknesses - you are not supposed to do every single question straight through.
One resource that's just as good as the 1001's for reinforcing concepts (and equations) over and over again until you can't get them out of your head is the Princeton Review Science Workbook - it has the same type of stand-alone questions as EK 1001's (some identical since Jordan used to work for TPR) plus it has passage based questions (EK 1001 does not).
For efficiency, I'd recommend the TPR science workbook - if you have a lot of time, you can try out the 1001's but there's no real need for all those questions.