In general, the headset worked well. The lack of buttons - there's only one here for pairing, starting and ending calls and redialling - makes it very easy to operate. It's a little annoying at first not being able to adjust the volume up and down but once you've found the right level that's not too big a problem, and it means there's no fumbling around trying to figure out which controls do what.
In tests on various phones I was able to make myself understood clearly without having to shout as if I were on holiday in a southern Spanish seaside resort. The headset connected reliably without any interference and you should be able to get a decent fit, too, with four sets of rubbery ear fittings provided.
But it's not perfect. Sound quality is far from the best I've heard. Don't get me wrong, it isn't completely awful; just that a bit more refinement wouldn't have gone amiss. Voices were clear enough to be understood, but they had a hard, rasping edge to them at all times that made long calls more tiresome than they should have been. It's disappointing because, as a Bluetooth 2.0 device, audio quality shouldn't be limited by the speed or reliability of the wireless connection.
That single button could be more responsive, too: it takes a good hard prod to activate, and while this prevents accidental calls effectively, having to push the headset hard against the side of your head to pick up and end calls is hardly comfortable.
Still, that's not enough to completely put me off the Bluetrek BIZZ. You may view the microSD card reader as just a gimmick, but I can see it coming in handy for business users of smartphones in particular. The fact that it can be charged without a cable or mains adaptor is a boon, and it's on sale at a very reasonable price. It's just a shame about the sound quality issues. If those had been resolved I'd have no hesitation in recommending this clever little headset. As it is, however, it ends up with a reasonable but not outstanding score.