I have been practicing XSZ for about six years now. Initially the version taught by David (Verdesi), but the last years my main teacher has been prof Wang Ting Jun, who is also one of Davids teachers in XSZ.
There are some differences in what Wang teaches compared to the version David gives as part of his foundation training, but in large it is the same form. To my knowledge, the version found in Zhineng Qigong is also basically the same form, but done quite a bit smaller and also more simplified.
XSZ practice can by quite physically demanding, since the objective is really to prepare the body for the sitting practice, but is the best system I have found for opening up the joints and tendons and promoting general qi flow in the body.
There are several teachers in Sweden that offer classes in XSZ, but if you would like to go deep in the system I recommend coming either to the retreat with professor Wang (we host him for a nine day retreat in Sweden end of March-beginning April), or going to the seminar with David in Denmark this summer.
For the retreat with prof Wang, some previous knowledge of the form is required, but I think there will be a beginners week with Jette in Denmark prior to the seminar with David.
More info can be found on http://www.qigonginstitutet.se/ (unfortunately only in swedish) and http://www.chikungskolen.dk/english/index.htm