We get this question a lot here and it's a great question to ask. I'm going to give you my honest opinion and hopefully it answers your question by giving you some insight into where these reviews are coming from. First off, I wouldn't put much weight into other traders reviews to begin with for many reasons. Mainly it's easier to come across negative reviews than positive ones because people who have had a bad experience are much more likely to go through the effort of writing a review than those who still use and enjoy the exact same service year after year (I've traded with FXDD for 2 years but still haven't bothered writing a review). The reason this also happens is because in most of those cases you have a really naive trader making some terrible money management mistakes due to their own inexperience and mismanagement and then over-exaggerate the frequency and duration of such mistakes in order to effectively get revenge on that broker. This is easier to spot when reading the review as an experienced trader than it would be for a novice one, but here's some examples of phrases or statements to watch out for as a red flag for a trader who just got burned from their own ineptness:
1) anytime the phrase "blew up my account" or "the trade closed all of a sudden and I lost XXX amount" or "I made XXX amount and then one trade went against me and they wiped out my account"- this is also known as a margin call or over trading which is always your fault every time it happens, since proper money management prevents this type amateur mistake. Look for the keyword "stopped out" in the review.
2) Any reviews written regarding just the demo account since who cares how well your fake account experience went... it's a demo!
3) Claims that the broker is manipulating the price action are the most lame due to how easy this is to check into on your own. I always use more than one price feed from alternative sources and thus can cross reference a bad beat (a trade that went against me and stopped me out before reversing back in the original direction). If you see slippage of any considerable amount on a repeated basis and especially during low market volatility THEN you can claim the broker is manipulating the price feed.
4) Reviews that look like they took less than 5 minutes to type up and sound more like a teenager with bad grammar than an educated trader can also be written off because if you truly had a case to make against a company that you claim took your hard earned money and you are now warning the masses about wouldn't you also have plenty of relevant facts to support your claims? If not, then what good is your review anyway?
I'll stop there because my biggest point is that the reviews are just a superficial glimpse of the brokers at best. They should not be considered absolute fact, they aren't written by a professional trader most of the time, and like I said before it's easier to write a review when things go bad than when they go right. Ultimately you should investigate the broker's history and background, how much money do they have on reserve, are they an ECN broker, and who are they regulated by? From there, you should simply try them out by making a small deposit and small withdrawals as you see profits and see how that process goes; the more you get to know them the more you can deposit. There's no reason why you would invest a large amount of money into a broker you hardly know about. It's in the brokers best interest in today's forex market to build up a solid customer foundation and not to take your money and run. This industry is growing more now than it has before, so a wise broker will not simultaneously rip off one guy but not the other.