I'd be grateful for up-to-date opinions on the following:
Mysite.co.uk is highly listed in Google - because it's full of info and Google has, in its roundabout way, recognised this. Trouble is, Mysite.co.uk has poor SERPs in the more 'primitive' engines that would probably like to see just a few headlines and links and less text.
I own Mysite.com too - but have never used it. I'm tempted to optimise this for the primitive old engines out there. I don't intend to get up to any tricks like duplicating content. But does anyone foresee any penalties in such a doorway - consisting of a simple optimised page that simply provides links to Mysite.co.uk.
You can rank well with Google based on good content, decent PR, a good number of inbound links and relevant anchor text, but you can also rank well for the same site with other engines.
Though link popularity may still be factored in, for the others, the weight isn't on the external factors in the same way it is with Google, so you have to employ some good old-fashioned honest & basic on-page optimization techniques.
I'd try that first before bothering with any additional domains. There's no reason why a good site can't rank decently across the board. Maybe not equally with all, but I feel it's safe to say that if a site is optimized and/or doing well with Google, if you optimize individual pages for Inktomi you won't be far off and can do well with both.
People can get so wrapped up with hunting links and PR that it's easy to forget about search engine optimization. Clean, quality optimization works. Maybe the search engines would just as soon people did forget about that, but we're here to remind them every so often. ;)
Read Google's advice to webmasters: [google.com...]
"Avoid doorway pages created just for search engines"
Google don't like doorway pages because they are bogus content. They would much rather index your REAL content as best they can, and in your case it sounds like they're already doing a pretty good job of it.