Okay, so as the OP, here's a quick summary of where I'm at.
I've been on the hunt for some BT IEMs for a while, but without much success. Sony WF1000X have been roundly slated, Zolo Liberty's have varying reports with a lot of people talking about dropouts. Bose SoundSport Free have good reports, but they're too open-backed and unwieldy. Bose E8s seem to have the best reviews of sound quality and connection stability but they're fiercely expensive and still suffer occasional dropouts, apparently. The other problem I have is that I have a set of Sennheiser IE80s with custom-moulded sleeves, which give amazing sound, comfort and noise insulation - and I didn't really want to give them up. So I abandoned the idea of wire-free IEMs, and when they were on discount last month I ordered a PlusSound Exo BT Cable.
PlusSound is a tiny company with a small number of employees, but they're extremely responsive to emails, and customer service is superb. Because of their size/popularity the build time is quite long - it was 10 weeks from when I ordered to when it was delivered.
After a few hours' use, here's my impressions.
- Comfort: excellent. The controller/BT unit looks unwieldy but is unnoticeable in real use because it's so light. Controls are simple. Weird thing is that on my cable the 'up' volume was at the bottom and vice versa, but it's no biggie.
- BT connection: seems rock-solid so far. At home, on the train and walking down the street, I've had no dropouts at all so far (2-3 hours use). When trying out how to wear them (cable under the chin, or round the back of my neck) I found the latter resulted in a poor connection, but I've no idea why. Looped under the chin it's unbreakable, regardless of the pocket I have the phone in (Galaxy S7E). While getting breakfast in the cafeteria I left the phone on the side and walked over to the cutlery stand - about 20-30ft away - and the connection didn't drop.
- Sound quality: very good. Drives the IE80s really well. Bass actually seems to have a bit more oomph than with my 3.5mm cable; I'm guessing the PlusSound DAC is slightly better than the S7's. Really pleased with the sound, and so far haven't been able to hear any BT hiss at all. A few test tracks ('Fields of Joy' and 'Sister' by Kravitz, '1984' by the Eurythmics, and 'Release the Pressure' by Leftfield) all delivered with clarity and gusto.
- Battery: haven't had a chance to test this fully, as I've only used them for a 2-hour stint so far. But no concerns as yet.
- Video Lag: This was a big concern to me, because I watch a lot of movies during my commute. First attempt was pretty awful - a DTS rip playing on VLC for Android and the sound was about 2s out of sync. However, Netflix shows played with perfect sync, and when I tried Archos Player I could use the audio delay setting to get perfect sync. Downside is that Archos doesn't support all codecs. Eventually, I've switched to MX Player, which has audio sync settings - but even then it was still impossible to get the sound and video to match. The solution was to turn off hardware decoding on the audio, and then everything lined up perfectly.
To sum up, very pleased. All the quality and performance of my choice of IEMs, plus the ability to continue using my custom sleeves, but without the hassle of a long cable, is a total win.
PS: Unfortunately, the first BT cable I received turned out to have the wrong connectors (they were for Custom IEMs/CIEMs, instead of Sennheiser IE80s) but Christian at PlusSound rectified it for me quickly and sent me a complimentary replacement. Rather than just let them sit in a drawer, if anyone in the UK has CIEMs and wants one of these cables, email me (mark@otway.com), and we'll sort out paying PlusSound something, and I'll post them on.