Hello,
I'm a private webmaster and author of a bilingual photo blog and played around with several language plugin solutions and used each of these plugs several month before giving them up. First I did a single install of my blog trying to tweak the life with plugins that are linking and switching my articles from German to English depending on what was chosen by the reader or read from the browser meta data. None of these plugins in combination with the WP WYSIWYG editor did a perfect job, especially when it came to using tables in my posts or special image alignments I like to have. All of the plugins did made usage of special language tag within a single post.
Finally I ended up with XILI language. The major change in using that plugin is that each post was existing in one language so no more tweaking around. The best results I ever had and some of my blogs and hosted websites for my friends still use this free (and in my eyes the best language plugin out in the WP world).
But for my own photoblog I wanted more: I wanted to have different images (as my images do contain pieces of text and so I do have different images for each language).
So I ended up with two domains and two blogs but I used the WP multisite feature, so I only need to update all plugins and the WP core source one time.
So I was writing two separate blogs (each for one language, each having it's own domain) more or less I wrote in my mother language but would love to have a better user experience when it comes to switching between languages. Last but not least it would be great to push myself a little bit to translate my posts (where it makes sense) a bit mor comfortable and force myself write bilingual. I learned about the XILI language multisite plugin and was a bit concerned about pricing and if that plugin would make sense even on my private site. And my both blogs already had over hundreds of posts. I decided to give it a try and I have to say as like XILI language for a single blog/site the XILI language for multisite is tremendous and within just a few hours I had connected my blogs/posts/categories and tags. It is very easy when writing a posts to create the associated article in the foreign language. I'm using two different domains, can use the different images, can even use different themes if I would like, can use different advertisements link to different targets etc. etc.
Even though that the XILI language multisite plugin is a paid plugin it is worth each penny to get, I'm also using a paid version of the theme I use. I have learned if you like to have an easy life in administrating or for your blog visitors it is worth to spend a bit money and save time.
So I would recommend to get in touch with the developer of the XILI plugins and chat with him and see the options.
Cheers
Yogie
(and as Marcel wrote have a look at http://dev.xiligroup.com/?p=1961)