For me it's been kind of a "soft restart" in HC in D2R. My D2L 99er Barb provided a starter pack of items and runes, but otherwise my current Diablo activity is just HC farming and getting a Guardian sept in D2R.
As for SC, I've kept all of my MF/RF tournament characters in D2L for two reasons. First, as a general rule it's more efficient/faster to farm there. You can't go back, so the safe bet is to stay in D2L. I'm a bit of runtime/efficiency nerd when it comes to tournament situations such as MFO or RFL. Ofc actual results are mostly luck-based, but I just wouldn't like the feeling of being slower just from playing in D2R rather than D2L.
Secondly, I'm not sure what SPF tournament rules will look like in the near future, as in to which degree D2R is allowed, whether it's separate from D2L running etc.... so I'd rather retain the option to play in D2L.
Also, many SPFers have not gone to D2R yet for various reasons, so I'd like to be able to participate in D2L activity in any case. I can imagine at some point down the line everyone will just play D2R. At that point I guess I'd just migrate SC chars as well... Restarting (kind of) in HC is fine for me because I had never really played HC in D2L. But when it comes to SC I'm too old to restart completely
no way I'll ever get to the same level of "endgame" min-maxing, and that is what I mostly enjoy when playing SC.
I can imagine Blizzard is trying to do something about the loading times. Especially for bnet HC players that seems to be an absolute dealbreaker. So in short, if they manage to optimize them somehow and SPF tournaments are interesting from a D2R perspective, that's when I think I'll migrate everything and switch to D2R for good.