I did an upgrade to leopard (new imac and did standard migrate from old) and had to get the latest version of missing sync 6.0.2...
I sync to palm tx so can't say for sprint phone but if missing sync says ok.. then it should be good. I've had good experience w/missing sync and decent support via email, no crashes.

Realize missing sync says somewhere that NUDC not on the "accepted" list so there may be issues but I've had minimal problems.. I like missing sync.
Missing sync lists loads of conduits... the main "trick" is knowing what conduits to use so be sure to read documentation on that- I'm not using any of the mark/space conduits except memopad (notes didn't work right w/me) and I did select the now contact/up to date conduits, plus other conduits listed that I use like password wallet, timecopy, docs to go, install, etc.