Jetpack is a great plugin and the stats it provides is also wonderful. The only thing I would suggest is you don't accident activate the part called Photon which which saves all of your graphics on the wordpress cloud server. There is no longer a "deactivate" button for this feature so once you turn it on you are screwed. And it WILL slow your site down. Their claims of speeding thing sup is a horrible joke. And once you have it turned on and can't turn it off, you are forced to have a horribly slow site, which also greatly hurts your SEO or you have to just delete Jetpack all together.
Right now to pull up a simple 53kb image takes 9 seconds. 9 seconds may not seem that long to some but anyone who has sat there staring on a screen for 9 seconds realizes how unacceptable that really is and since you can't turn off Photon once it is turned on I just wanted to warn you all, don't accidently turn it on!! _BIG MISTAKE_