If most reviews are good with only one "bad" I would generally chaulk that up to someone had a bad day...  I've met one or two providers who had good reviews and for whatever reason we didn't click.  I wouldn't tarnish her good record if the service was good.  

Consistently rated "7's"...  I'd read the reviews to find out why...  In general I think if the lady puts in the effort, most reviews I've seen the reviewer gives them pretty decent ratings.  However there are so many highly rated ladies I want to meet that I probably wouldn't take the plunge...

Even the plainest women seem to get 8's, 9's and even 10's. 7 seems to be codespeak for "homely" and 6 means "butt ugly" in most cases.

I hate to be guilty of using a double standard, and I have gone on record stating that the numbers mean next to nothing to me, but I will confess that while solid 9's and 10's don't really assure me that a woman is hot, solid 7's will almost always convince me that she is rather plain at best.

Now if we are talking about performance, the same thing applies as well. Most women getting 7's either have VERY bad attitudes or limited menus. I don't give a fuck about Greek, really bi, or getting it on with multiple guys, but I won't see a woman who won't kiss, and only rarely will I book a woman that I know in advance only offers CBJ's. Fairly or unfairly it seems like most of the women who get 7's or below fall into this category.

But other info like .. she was hot.. but not into it.. or she refused to give me a BBBJ.. stuff like that.. will make me avoid a girl..  
Sometimes I will not do a review if an issue seemed to be unique to that day.. Like the girl that was as dry as the Sahara.. and it was obvious she was just doing her job.. aa turn off..or a nice enough girl.. who just does not seem to have a connection.. so it is hardly an exact science.. I don't want o put that sort of thing in a review and cause others to avoid her completely when it may have been a bad day for her.. One girl gave me a strep throat.. OK.. shit happens.. but I'm not going to put that into a review either.. when she saw me she probably felt OK..

If she wants 300 or 400 forget it, stick with the better reviewed girls.  

If she asks 250 or less you should not be surprised by YMMV.  You get what you pay for...most of the time.  Then again, if she offers a certain skill I might give her a try.

When I search, I'm looking for an overall average greater than 7.  Obviously I prefer higher scores, but generally I expect a nice session with 7s.  Generally on the performance side you can't score higher than a 7 without GFE service (like DFK or BBBJ).  Some girls don't provide those services, but if they're hot and fun I'll see them.  I admit to being shallow in that regard.  Also, there are some taste factors that impact scores.  For example, a lot of guys like the big Nicki Minaj / Kim Kardashian butt and I personally don't like that (I prefer smaller tighter body girls like Audrey and Savannah at RSG, Emma at Chloe's, and many of the Boston Asian dolls)

TER has yet to figure out a system to filter out excessive "grade inflation" -- i.e., half of the reviews are that 10/10 "one in a thousand" -- and most reviewers either can't do math, or are afraid to give lower reviews where merited.  7's won't phase me if I see that that reviewer has given 7's to women who I have scored higher.  Likewise, a 9+/9+ doesn't mean anything to me until I dig into at least 5 or 6 reviewers' other scores.  I think that TER needs to hire a statistician.  (Still waiting for them to do a simple "throw out the high and low scores" like they do in the Olympics, and/or a weighted average score that puts more weight on a woman's recent reviews, and less weight on those early in her career.  The do sometimes get better over time.