Doing Research Before Buying
You should thoroughly research any instrument you are considering. Reviews will help you avoid guitar models and brands that have known problems. There are many online resources for finding reviews.
Online Guitar Reviews
YouTube
Many companies and individuals are now posting videos of demos and reviews of various music products on YouTube. The people who post these videos will often answer questions that are asked in the comments, so it is a good way to get information directly from the manufacturer or someone who has played the instrument. The videos also give you an opportunity to see and hear the guitar in action.
For example, the Paul Reed Smith SE Soapbar is demonstrated in the video below:
Reviews at Online Stores
Many online music stores allow customers to review products directly on the product information page. Most stores seem to be fair in allowing negative reviews to be posted, but you should be careful if you rely entirely on these reviews. Retailers and manufacturers have an incentive to get rid of negative reviews, so you can never be entirely sure whether the reviews are entirely accurate. It is also possible that positive reviews are astroturfing by the manufacturer in some cases. There are no reports of this happening in the music industry, but companies in other industries have been in the news recently for this kind of activity, so just be aware that it could happen with reviews of music gear too.
Harmony Central
Harmony Central is an independent site that allows users to review nearly any kind of music gear, including guitars, amps, and recording equipment. Most products have quite a few in-depth reviews. Each review allows the user to grade a product in terms of things like sound, features, quality, and customer service. There are also reviews on older guitar models that are no longer manufactured. This can be useful in researching a used guitar if that model is no longer manufactured.
Guitar Forums
There are dozens of guitar forums where guitars and other music gear is discussed. Many of these forums have large archives that are perfect for research. If you are unable to find information on a particular guitar, you can always post a new question.
Here are some of the most popular forums:
Magazines
Most guitar magazines include reviews of guitars and other music gear. Many of these magazines have online archives where their reviews are provided for free.
Here are links to the review sections for two of the more popular magazines:
Note
You should always look for several sources for reviews. Never make a purchase based on just one review, because there is always the potential for bias. Reading multiple views lowers the chances of a biased review affecting your purchase decision. Ultimately, you have to play the guitar to determine if it is right for you.