First things first: Tripadvisor doesn't distinguish between guesthouses and hotels, so if you're looking for a fancy, high-end spa and resort, Baan Nud Kun guesthouse is not for you.
But if you're looking for a reasonable, clean, and quiet guesthouse, look no further.
Prior to traveling to Chiang Mai for a full week, my wife and I had spent a few nights at a slummy guesthouse in Phuket. We were absolutely thrilled to discover Baan Nud Kun. My wife had been arranging a room with Tao via Email, and we were pleasantly surprised to find that she had put us at the top floor, furthest room back (meaning that no one could walk by the window of our room. Very private and much appreciated.)
The room itself is small, but why do you need a big room when you're spending all day exploring and adventuring? The bed was very comfortable, the fan worked great, and the shower was hot. Perfect. They even bring two fresh bottles of water every afternoon directly to your door. Bonus!
The buffet-style continental breakfast is an awesome feature as well. Fresh fruit, cereal, toast, pastries, juice, coffee and tea. Also, the breakfast is a fantastic way to cut the cost of a meal if you're traveling on a budget.
Nud was super helpful. Any questions we had about anything, he was willing to guide us through it, or offer advice from a local's perspective. I really enjoyed chatting with him about his travels as well.
Very late one night, there was a loud couple who came back to the guesthouse drunk, banging on doors and knocking things over. Tao received a number of complaints the following morning, and it was a nice surprise to see that she asked the couple to leave the next morning. If you plan to party hard in Chiang Mai, consider looking for a place above the go-go bars on Loi Khor Road outside the walls.
Other great features include laundry service (Ignore the other reviews about laundry service. Just ask for cold water and half-heat and you'll be fine,) cheap bottles of Chaang yai, great WIFI (we had no problems the entire week we stayed,) and super friendly staff (everyone was always smiling!)
Add in the fact that you're tucked away on a quiet Soi (road) right outside of the Tha Pae Gate, and you couldn't ask for anything more.
I'd recommend Baan Nud-Kun to anyone looking for an affordable, clean, quiet, and overall pleasant place to stay in Chiang Mai. This was one of the best experiences of my trip to Thailand. Home away from home.