Most of the Big Six Traditional Publishers or & 7 if you count Harlequin have now started digital first lines for romance.Random House is also accepting unagented manuscripts in suspense and fantasy genres in addition to their romance line LoveSwept.
It is really unknown at the moment how much an author will be able to make from these lines, and how well they will do. That is not to say they won't do well. It is just an unknown how these lines will pan out.
The royalties on these lines appear to be....shall we say modest. They are less that what other e-publishers offer. Although I have seen no mention of what royalties Random House will actually be offering anywhere.
Avon Impulse and Forever Yours have lower royalties than older digital first publishers such as Ellora's Cave.
Some people say it would be worth it for the branding, editing and promotional push that the Big Six or Seven can give you despite the lower royalties.
Avon Impulse for example offers 25% on
net sales until you reach 10,000 copies sold and after that you get 50% net. E-pubs like Ellora's Cave on the other hand offer 40% of
cover price for digital releases when bought from their own website.
But these big publishers possibly have a lot of promotional pull etc.... Avon Impulse seems confident a significant number of Avon Impulse authors will sell over 10,000 copies.
Trident may certainly have a point about low royalties, but has it's own bandwagon to push. Almost no publishers give advances on ebook only sales. In fact Random is known to give advances on it's LoveSwept romance line, though I don't know what these advances are.
I think you (OP) said in your other thread you had difficulty getting any traction with sales going it on your own? So it's all taking a punt really.
You cannot submit to Ellora's Cave and many digital first lines unless you have a romance.
But Harlequin Digital Editions are also willing to look at what you write, OP (suspense, mystery). Not sure on the royalties there either probably similar to Avon.
http://www.harlequin.com/articlepage.html?articleId=1734&chapter=0