My list of functions in order of awesomeness:
1 Si: It would feel like the past and the present are actually part of a line. No more differentiation between me and my past selves.
2 Te: I'm now starting to use this one on daily basis. Its impressive. I can get all my extroverted stuff done. It feels refreshing, like a cold glass of water in summer time.
3 Fe: It would feel like understanding society from the inside. Like knowing what to said and do and get all the relationships in order. Fe it is the sexiest of the 8 functions.
4 Ni: Its pretty boring most of the time, but occasionally I get all the views of many people I consider wise (including some of my past selves) right in my head, simultaneously!.
5 Se: I like it the most because of sexuality. Also sports!
6 Fi: It makes me like all kinds of music. Also it lets me Know what I really want.
7 Ne: It makes me feel dissy and makes me take bad decisions.
8 Ti: It hurts like hell and doesn't works well. Also I'm quite addicted to Ti.
Si is awesome.
Sadly I will developed it for the first time around my 80's and Si is all about past experiences so I'm not going to have a good Si record even if I get to test it.