I’m dual booting Mountain Lion and Lion, been using ML nearly permanently since its release to Devs, until last night when it was acting weird when VPN’ing onto a client site, rebooted into Lion and it was fine, still running off Lion partition now and only remembered when I saw this… What does that tell you – nothing really ground breaking in ML.
Some people are reporting better battery performance and slighter better speed, especially with instant on, but its not really that noticeable.
In short, don’t stress about getting to Lion if its only to get to ML.