Where do I begin? I've been a full-time freelance writer and blogger for the past five years, during which I've worked with about six different companies. Of those companies, I can say that BlogMutt is the worst.
The pay is absolutely horrible. Writers earn a measly $8 for a 250+ word post, for which BlogMutt earns $17. So, while writers do most of the work, BlogMutt keeps most of the sale revenue.
BlogMutt also uses a format that similar to 99Designs, where multiple service providers compete to win clients. This is great for clients, but no so much for writers. Clients often reject blog posts for reasons such as "I've chosen a different post" or "I liked another post better."
Like other writers have said, BlogMutt will suspend your account without reason. After working with them for over a year, I was shocked to discover that I could no longer log into my account. They didn't tell me why my account was closed, nor did they return my unsold articles stored in their system (over $1,000 worth of unsold articles lost). I emailed them several times inquiring about my suspended account, but I've yet to hear back from their "support." What a professional way to treat your writers...
Unless you write strictly as a hobby and not a profession, stay away from BlogMutt.