Good things about the SoundSport Free:
1) Pretty good-quality sound (for Bluetooth).
2) Really comfortable "Stayhear" eartips. I love these on both the SoundSport and SoundTrue models.
3) Pretty quick to pair once you take them out of the case.
Not-so-good things about the SoundSport Free:
1) You look ridiculous wearing them (they stick out from your ears like Frankenstein bolts)
2) A little bass heavy. That's not so obvious from the above graph, simply because I've normalized all graphs at 1 kHz, where the SoundSport Free has a bit of a bump.
3) Like most of my IEMs, they tend to roll-off a bit before 10 kHz. (The ER4XR had an excuse for this - they were measured with Comply P-Series Foam tips.)
4) The SoundSport Free operate with the left earbud acting as a slave connection, driven by the right earbud and while the connection to the right earbud is generally good, the connection to the left earbud will randomly drop out. Sometimes it drops out only for a second or two - other times it drops out permanently and you need to put them back in the case to re-pair them. There doesn't seem to be any pattern to the times when they work and the times when they don't. BT generally doesn't like transmitting across a large volume of water, and your brain is about 80% water. Also, is it really completely safe to be sending radio waves from the R to the L bud - which is literally a connection directly through your brain? Even though BT uses far less power than cellphones, you're using them right on your head (in this case, right through your head) and potentially for much longer periods of time. There have been some recent studies that question whether these radio transmitters are really safe. Ok, I'll take off my tinfoil hat now...
5) Lag means they're awkward for watching videos - the audio doesn't sync with the videos. Also, I use headphones for language-learning apps and the lag means these earbuds cut off the first half of each spoken sentence.
6) When cycling or running, the way these earbuds protrude from your head creates a couple of small cylinders for the air flow to negotiate. Anytime you put a cylinder in a cross-flow at a high-enough Reynolds number, you're going to create turbulence. Although you won't have to contend with microphonics from cable noise, be prepared for some significant wind/buffet noise.
7) When taking phone calls on these, there's no option to get audio in both ears - only the right ear.
All-in-all, I'm quite impressed with them, considering they're bluetooth. If you come at these from the perspective of a good-quality pair of wired headphones, you'll probably be disappointed. But if you come at these with the understanding that Bluetooth is an immature technology which isn't 100% ready for the mainstream, then these are actually quite good.