I've been with them since before they opened for business two and a half years ago. Note that the following is only my personal experience, but I have been very happy with them.
Payment is typically monthly and happens on time, for values of "on time" that include it slipping by a few days when the staff are all at Romance Times, etc. Sales through distributors are not paid until LI receives the money from the distributors, so for example Fictionwise payments are quarterly and a couple of months in arrears.
The editing is not as intensive as I would expect from a big NY publisher, but it happens, and it's good. (If my editor moved publisher I might well follow her...)
Cover art is generally good to excellent (this matters), you get some input, and they are responsive if you hate it. There's the occasional absolutely dire cover, but it's occasional, not routine.
My sales figures (all m/m books, mostly sf/fantasy) vary from a few hundred to several hundred copies. My last book came out nearly a year ago, and the general trend of sales has been up since then, so I would expect my book coming out next month to do significantly better than the previous one. There are people selling a lot more, and some selling less, but the house is popular with romance ebook readers. The editing and proof-reading have been mentioned by readers on mailing lists as reasons to favour the house when buying books. My backlist books all continue to sell several copies each month, even the ones that have been out for over two years now. These are small press numbers -- you will sell a lot more copies through one of the big New York houses. But they are good numbers for epublishing.
The current contract is initially two years, after which it automatically renews annually unless either party gives notice. There is a one year option for print rights (which if taken up also extends the ebook term), but they explicitly exclude anything not to do with book rights. They have first refusal on translation rights and further books in the series/universe.
It is primarily an ebook publisher. There is a print programme, but they do not intend to take all books to print. Do not assume your book will be available in print. There are no fees, and the last time I checked the contract they were responsible for copyright registration on print editions.
There are a couple of the EPIC red flags in the contract (including the automatic renewal unless you explicitly give notice), but not ones I personally have an issue with. I don't like the reversion clause for getting your right back during the term of the contract (it's restrictive and it involves a fee), but at least there is one, and you can always give notice that you won't be renewing the contract come annual renewal time.
I don't know what the current response time is for the slushpile, although I believe they're still managing within a month or so. Time from turning in a complete draft manuscript to publication varies (my novella and novel length ones have been anywhere from six weeks to six months), but is about to get longer to allow more flexibility in editing and proof-reading. It will still be significantly shorter than your typical print publisher. It's not first in, first out -- for example, my next two books will come out in reverse order, because the second one finished is a) themed to a specific date Real Soon Now, b) a lot shorter and thus a lot quicker to get through editing. So my editor's working on that one first.
You can see my books here:
http://www.loose-id.net/searchresult.aspx?CategoryID=30
If you want to email me, feel free:
[email protected]