I've been using one since about 2004. I bought it originally for the very reason the OP cited - the mic cords on the Astro portables we use are a PITA. I hate the way the mic cord it feels if I run it up my back and around my shoulder, and if it goes around the front side it dangles right over my spare mags & stuff. They have updated things since they first came out, enough so that when I purchased a cradle charger for my mic I had to get a new mic because the original one ( I had an EARLY release model) didn't charge right. Freelinc was very good about it when I called - they next-day shipped me a new mic and adaptor for free, even though I had cut the toggle switch off the old adaptor. (You'll see why I did that below).
I mostly use the Freemic, but I have a Freemotion earpiece too. I charge the mic about once a week on my days off and the battery lasts just fine. If you're on a foot beat or a post where you don't have a car radio & are working off your portable constantly, you'll want to charge it every 2-3 days. Reception is fine, nobody has ever told me they couldn't understand me. I've got a plug-in ear piece I run under my shirt to the mic that I use too. Works fine.
The one design flaw they have, if you want to call it that, is the toggle switch on the adaptor/transmitter that attaches to the radio itself. Depending on how you wear your radio, the toggle can get pushed to the "off" position by the seat cushion in the cruiser, etc. They really should have gone with a flat, sliding type of switch for this, and I've mentioned this to them when speaking to their customer service people. Regardless, I nipped off the toggle so there's just a nub I can flip with my fingernail. Works great now, and stays "on".
Another feature I like it the transmit button on the radio adaptor. You can stand with your hands at your sides, hit that button, and transmit without reaching up to grab your mic. Every once in a while that comes in handy if you want to surreptitiously say something to another unit without being obvious. Combined with the ear piece, the bad guy has no idea you're plotting against him
As for the Freemotion earpiece, it works fine too, I just don't like the idea for patrol - too easy to come off when running or fighting with someone, or if you get hit in the side of the head. I do own one, however, and use it on surveillance or plainclothes assignments. The great thing is that without a cord, the portable can be carried in a backpack or wherever, and the earpiece looks like its for a phone. We do this when riding bikes in the parks trying to spot people breaking into cars. Both the mic and the earpiece can be set to be voice activated too.
Freelinc at one point was talking about making something like the freemic, but without the speaker capabilities - in essence, just the transmit button, a mic, and a plug for an earphone. Would be a lot smaller than the freemic (which itself is smaller than a Motorola Mic), and seemed like a good idea to me. That idea seems to have gone by the wayside,however.
To sum it up, they have very good customer service, their products have been reliable for me, and I'd hate to have to go back to a corded mic.