I've used everything under the sun. Lemon oil is mostly petroleum distillates with lemon scent so it's more solvent than oil. Normally I prefer to use Naptha for cleaning and a separate product for oil (however, I've since changed my ways...read on).
Bore oil is good as a conditioner but it's on the thick side so you get the feeling that it doesn't penetrate much which isn't anything to lose sleep over but worth noting. Gerlitz Guitar Honey is very nice because it's light and not too oily (I believe Sadowsky started using this on all their non-maple fingerboards). Fret Doctor is the best conditioning oil I've tried. It penetrates well and really does a nice job on rosewood and ebony.
With all that said I just discovered a product called Gorgomyte and it is by far the easiest to use and delivers outstanding results on both the frets and fingerboard. It's a chemically treated cloth which polishes the frets, cleans and conditions the fingerboard all at the same time. Once you wipe down the entire board you buff the residue off with a clean cloth/old t-shirt and you're left with super shiny frets (puts steel wool to shame) and a clean, conditioned fingerboard.
http://www.gorgomyte.com/