I've put a small write-up about using the new BME280 sensor to measure temperature, pressure and humidity here:
Some graphs can be seen here:
where I have two RPi cards working next to each other at the moment to compare the results from two sensors, prior to taking the second RPi downstairs, knowing that its results are reasonably well related to the first RPi which will remain upstairs.
I would love to know how accurate the humidity reading is - low-cost devices I've played with show humidity values of 43%, 47% and 49% when sitting next to each other, suggesting that the +/- 5% specifications of one of the devices is a realistic value. Will the Bosch BME280 be any better? The data sheet specifies +/- 3%.
My thanks for Adafruit for making the sensor available and help on their forum, and to Pimoroni for stocking and delivering them.