My overall First Class experience on the 737-800 was very good. The crew was friendly and attentive and the seats were comfortable.
If you are traveling alone, consider sitting in the first row - despite the restricted space to stretch your legs. If you are traveling with someone else, I suggest sitting in the second row - you’ll get pre-flight drink service before rows 3 and 4, you’ll have underseat storage and a power outlet, and you won’t be the last to order your food if they start in the rear of the cabin (sometimes they run out of options and you get what is left, even if it isn’t what you wanted).
I recommend Delta’s First Class product to anyone traveling domestically and with the means to do so.