I have seen many reviews and majority of them are negative, They are saying there are many loop holes, unanswered questions etc. I will keep it simple, Yes it's true that their are many unanswered questions and may be loop holes(I personally don't know what loop holes are there..) but that's given considering it is related to time travel and stuff, Other thing is series is ended with many unanswered questions so there will be a sequel for sure and they made this series keeping that in their mind, most probably question will be answered in upcoming seasons depends upon how many seasons they have in mind, So just judging the series on the basis of this is not right,
I my opinion give it a shot, I personally liked it and I think it is story which will become more interesting in future.
For those people who don't like cliffhangers, Don't watch this or may be wait till whole story is over and then watch the whole series in one go, so you won't be on a cliffhanger for long...
Hope this review helps..