Well I would disagree of course that SSPX sacraments are invalid, myself attending an SSPX Mass and receiving the Sacraments there. In fact I had a conditional Confirmation, and made a general confession since I did not believe my parish priests absolved me properly (they told me certain sins were not sins, gave no penance and did not say the words of absolution- this occurred many times). I would not have done this needless to say, without studying whether or not the sacraments administered by the SSPX were valid. If I had any doubts, I would not go there for confession. This was an issue I studied deeply before deciding to attend an SSPX Mass, since I had heard some people say their Marriages and Confessions are not valid since they do not claim any jurisdiction. Others of course disagree with me, and I have debated the issue many times. It is indeed a complex issue, once all of the arguments from both sides are on the table. One thing I would say though, is that certain sins require the permission of the Holy See to absolve, and this permission has been given a few times it was asked for by Priests of the SSPX. Also, those who leave the SSPX are not required to make a general confession or confess sins absolved by an SSPX Priest.