Hi orkan,
Welcome to the site 
I’m assuming that you’ve read the mattress shopping tutorial here but two of the most important links in the tutorial that I would especially make sure you read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort” and PPP (Posture and alignment, Pressure relief, and Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists (based on all the parts of your personal value equation that are most important to you).
There is also more about the Tuft & Needle and some of the other simplified choice mattresses in post #2 here of the simplified choice topic.
Tuft & Needle is certainly one of many good quality/value options available to you and I’m looking forward to finding out what you end up deciding … and of course any comments or questions you may have along the way as well.
Phoenix