As of October 2009 picmac now resell fotolia and dreamstime images along with a 'luxury' macrostock priced collection from image source, this in addition to their own collection from contributing photographers.
Pixmac currently offers more than 7 million images to buyers, most of which I assume are sourced from fotolia.
If you are a fotolia photographer then you will likely already have your work for sale on through pixmac. They do this via the fotolia reseller API which you can opt-out of on fotolia if you wish, pixmac are also listed on fotolia as an example site in their api documentation.
In the past pixmac has received some quite significant criticism from photographers, when launched the site was full of shocking spelling errors (who am I to talk!), including those in the terms and conditions, e.g. "in no case shell be liable for any demages"; at the time this and the fact that photographers were confused when they saw their own fotolia images being resold without explanation lead to a general feeling that pixmac was 'yet another startup microstock'. Pixmac have worked had to rid themselves of that label with photographers, but it's important to realise that new buyers don't come with these preconceptions.
Comment
My initial review of pixmac (nov 08) was not entirely favourable. I uploaded images only to test the waters, there was a general feeling in the microstock contributor community "why upload here if you are already on fotolia?". Almost a year later I still don't have a lot of concrete information on direct sales from pixmac, but less than 12 months has seen some big improvements.
I'm continuing to upload and see what happens, and will update this as I go. As of Q3 and early Q4 2009 uploading is reliable, as is review time (earlier this year the site still had several teething problems and review times was unacceptably long).
It's a nice looking site (if you like pink) but quite a few fotolia affiliates have opened up why is this one any better? Marketing for a start, and continued innovation like improved search and streamlined buying process. Most agencies have not caused confusion to microstock photographers as they only resell images and don't include features for you to upload your own work in tandem; to reiterate what I wrote above, buyers won't be in the least be interested in the recent history of photographer opinions, they buy images they want if they find them at a price they are willing to pay.
Just to clarify the reselling point, anything you upload to pixmac will not in any way be connected with fotolia/dreamstime, the fotolia/dreamstime connection is purely one way, pixmac resell fotolia/dreamstime images and also their own images.
More details on the pixmac website

Clarification of data:
Vitezslav Valka (not verified) on Mon, 11/24/2008 - 10:27Re Clarification
Steve Gibson on Tue, 11/25/2008 - 23:33Thanks for your comments, I guess that's what you get for believing wikipedia.
If pixmac is so 'under development' then why has the photographer submission area gone live? Why were there so many, shall we say "promotional comments" about pixmac made on forums and blogs a few months back?
I thought what I had written was a fair view of the site as it stands at present?
Steve
Microstockinsider.com Editor
Trust me
Vitezslav Valka (not verified) on Fri, 11/28/2008 - 10:07pixmac strategies and results
Anonymous (not verified) on Mon, 08/17/2009 - 14:38Quick Update
Steve Gibson on Mon, 08/17/2009 - 23:45Thanks for the data, it mirrors what I see, I've had at least 5 months with 99 accepted images and earned nothing. (Edit Oct 09 - Had a couple of direct sales in the past few months, but still nothing significant)
Steve, Microstockinsider.com Editor
get 10 credits (value of $20) for free!
Anonymous (not verified) on Thu, 09/10/2009 - 13:25