I have never painted in oil other than Genesis so to compare the two mediums is something I cannot do other than to say I found frustration with the SLOW drying time of the Genesis and forever having to "dry". Once you have blended something it is done.....so I have never fully understood the reason why one needs to have a 3 day open time? I also have found in conversing with some of the women who do work in oils...their major COMPLAINT is the open time...in that it is TOO long. I guess it all depends on the artist which is something that I have always understood but other artists feel that the only GOOD artist is an oil artist.
Brenda Harris carries a line of 3 Mediums that I LOVE. Slow Blend, White Blend and Clear Blend and I have found that these mediums really allow for a smooth transistion of colors when blending, shading and highlighting giving you quite a bit of open time which, for me, seems to be just about the right amount and if I need to speed up the time I have a very small travel hair dryer at my station that does the job in ample time. http://www.brendaharris.com/ I have been using her mediums for about 4 years. I don't use them ALL the time but when I need them, I need them, and I have them to grab. Brenda also has some gorgeous pattern packets and her use of a sea sponge for creating foliage is worth a video.
Another medium that I have recently begun using for different "effects" is JoSonjas retarder and antiquing medium which also has its place on my paint table and is wonderful for layering color. I love using washes/tints of transparent colors. This can be easily accomplished using Clear Blend without having to purchase special products.
I am one of those painters who feels that different mediums have special uses so I don't "stick" to just one for EVERYTHING. I don't feel such a medium has been made to provide this luxerious freedom and I have a tendency to stay clear of "hype" and use what works the best for me.