Happy Birthday To Me started off looking promising, with a girl getting her throat slit, and the pace moving along nicely. But then things started to get confusing, as the girl has flashbacks, and you're left trying to figure out how this fits into the storyline. At the end of the film it starts making a little more sense, but then suddenly things take an unexpected twist (a twist too far if you ask me) and the film gets too far fetched, resulting in a spoilt film. If they had of left the twist as it was rather than adding the ridiculous second twist, it would have been a much better film. However, there are many good scenes which get points from me such as the flashback of the car falling off the bridge - it's very well done and we get to see the car falling in at different angles. The acting from Virginia's mother is also superb for her brief appearance. There are some unusual death scenes too although I must have seen the cut version because I didn't get to see much of them.
Overall, this film could have been a lot better without the elements that make it confusing, but it's still worth seeking out and is better than a lot of slashers out there.