I dual boot lion and mavericks on a mba. I use airplay mirroring with extend desktop on this, so mavericks is good for that. But sometimes I still have to use lion for some hardware that has drivers that won't work with mavericks.
I also used to dual boot mountain lion and mavericks on a mbp, but have since deleted the mavericks partition on the mbp and replaced it with 2 virtual machines of mavericks in parallels, 1 for 10.9 build 13A603 golden master which I will never update, and the other is 10.9.2 beta build 13C62 and this will get updated all the time with all the betas.
I use the golden master to find direct links for combo updates for the betas. The combo won't show up in the mac app store if you use 10.9.1 or 10.9.2 (at least not yet anyway).
I found mavericks to be somewhat more buggy on the mbp than on the mba, so for now I will still use mountain lion on my mbp.
