I know that here at SE I cant ask recommendation of products and so. I have a printer that I wanna buy and I want to know if it's good. Where should I post this question in order to get some smart people to take a look?
Great question! 3DPrinting SE attracts a lot of new Stack Exchange network users, which unfortunately can come with questions that don't always meet the Q&A style for the network that this site tries to uphold.
Questions like this are probably best asked in the Chat room. Currently, it's not very active, but hopefully if we have a few people interested in these more "off-topic" questions the activity will pick up. Pings are going to be a very useful tool if we're going to try and utilize the chat window more. Pinging some of the highly active users may help get quality answers to those off-topic questions.
Some of your question could be acceptable. What you want to avoid is "questions which are too broad, unclear, incomplete or primarily opinion-based". That still leaves lots of other acceptable questions to ask like what printers have a specific feature or whether a specific printer has a specific feature. Note the word "specific".
There is also a Hardware Recommendations SE Beta that may work for you.