It depends. It is very easy to upgrade an unmodified board, so if you aren't going to be installing any hacks on your board, then I wouldn't worry about starting with 3.6.8. It also depends on how long you want to wait to start your board. As far as I know, there is no set release date for 3.7, so you could end up waiting a while if you want to wait for 3.7 to be released.
well... i like vb3.7... but i have lots of modification installed on my board... so it will kinda hard for me to upgrade..
yet whhen it come out... there will be no mods or skin for it...