Basically you should not be on the cutting edge...
If you pick Liferay 6.0.6, for example, it is a pretty stable foundation that is not going through all of the transitions 6.1 is still in.
I don't think the 1.0 version is out there, but it looks like sourceforge has some version 4 (and maybe version 3).
The farther you go back, though, the older the web technology is going to be (version 4 used prototype, version 5 used jquery, I don't know what version 3 used). You're not going to find a lot of support on the forum for older versions, either, and I'm fairly certain you can't get paid support from Liferay for any of those, either.
My suggestion - go w/ 6.0.6 CE. Give 6.1 a wide berth until the dust settles on the many new features and complaints/tickets about it subside.
I am wondering where the people are going when they need to ? We've encountered too many issues which won't be addressed any time soon and we're convinced that your 'portlets' can't really coexists with AUI and some CSS & caching aspects.
Well, we're not going anywhere, certainly. But I'm not doing any significant coding using AUI. My portlets are 90% based on Vaadin these days as I don't have to worry about many of the things you're probably having problems with.
Maybe instead of a Liferay version change you might consider a switch in your underlying portlet foundations? Try Vaadin or Zk, try JSF (Icefaces, Primefaces, etc.) and see if any of these alternatives work out better for you.