I have yet to find a "complete" spinning service that creates spun articles that meet my expectations.
Most services that offer spun articles at 75%+ unique will usually fail at some level (at least it did for me) because the work is outsourced to lower quality workers (how else does the service provider make money?)
Quality article spinning is something I've been looking a long time for. It's my most time consuming task and the hardest service to find (one that meets my expectation).
A spun article can fail for any of these reasons:
1) Original article written is bad quality (I'm guessing most services outsource this part to their writers for $1.5-$2.5 based on the quality I've seen)
2) The rewriting is bad quality. (This happens when the article is rewritten for the sole purpose of spinning. The quality is horrendous)
3) Bad spinning. Even if the spinning itself is good, due to the 2 points above, the resulting "super spun" article is going to be pretty shitty.
I no longer hire services that make super spun articles for me anymore. I've started doing it myself because I got so frustrated at how unreadable my "readable spun articles" were. Sometimes I'm too embarrassed to even post it as my tier 2.
The best way to get highly unique spun articles is to break down the steps and find someone good at each stage.
4 Simple steps I follow now (working great so far):
1) Purchase a well written article based on my keyword -> $5-$7. Try to use a writer you've used before that delivers good quality
2) Go to iWriter and select "Have articles re-written" and get 2 rewrites -> $4.25 x 2 = $8.50. In special instructions, mention that you want the sentences written in completely different structure from original but you want the sentence count to match and remain the same. Hint: With iwriter, you only have to accept re-writes that are good quality...
3) Go to fiverr and search for a manual article spin. Order a seperate gig for the 3 articles (original + 2 rewrites). $5 x 3 = $15. Make sure the gig offers the spintax (some won't for whatever reason). You only need word/phrase level spinning here. I recommend trying out different gigs until you find one that provides a nice readable word/phrase spin. (I value readability over uniqueness here because if I need more uniqueness, I will simply order more rewrites).
4) Take the spun articles, paste them into a separate Microsoft word document.
Press ctrl+F, switch to word replacement tab:
Search for all occurrences of (without quotes): "^p" and replace with "^p^p^p^p"
This replaces all the paragraph breaks with a bigger paragraph break.
Next you want to search for (without quotes): ". " and replace with ".^p"
This puts all the sentences onto a new line. Now all you do is simply take each sentence and put them together. Takes about 5-10 min.
Voila! A high quality, relevant, readable, and grammatically correct super spun article for under 30 bucks. It's well worth it if you're serious about your business. I do this for my tier 1 and sometimes tier 2. Never had a problem getting the articles indexed and building up PR. Easy way to get unique high quality contextual links back to your site. I also recommend setting up blogs that you post all your high quality tier 1 articles to. They really start to build up authority and natural links since these articles offer real value.
I also use wordai now to spin my tier 2/3 articles together sometimes. The quality is pretty good but it's still "spun looking" and has awkward phrases for certain topics/niches/articles. But I would highly recommend wordai too if you're not particularly keen on having super good quality. I don't use it for my tier 1s though because my tier 1s drive traffic too and not just act as backlinks.
Hope this helps someone out there. I know I've been struggling to find a good "all-in-one" spinning service for a long time (never did), so I'm assuming others are going through the same.