The build quality is perfect, the pot shafts and main case are sealed by o-rings and the speaker membrane is waterproof. It would not probably survive a drop in the water, but there is no need to be afraid of some dirt or rain. And another line of defense (a polyethylene bag) makes it weatherproof to a very high degree. There are two things I do not like. First, a two piece pole assembly is not aiplane travel friendy. Second, there is no choice of coils, you have to stay with one. I have learned to prefer 12" sized DD coils and I think such a coil would suit the machine even better than the default concentric 8" (which is not bad by any means). The headphone jack is 1/8" sized, there is no volume control and the left and right channels are wired in series - and that limits you a little with the choice of headphones, which I really recommend to use all the time. A cheap PC-type headphones work fine, however my favourite single-eared head set does not for the reasons above.I have tested the machine on pastures, fields and beaches. The depth is average and I rarely dig anything interesting below 8" (20 cm). It depends really much on the soil type. The range of scanning speeds is very broad from very fast to very slow, you rarely miss anything. Pinpointing with the X pattern is really accurate. The machine is really hot on small and conductive objects (read silver, copper and even gold:) The discrimination is really working well, after using another machine in the same pasture I have realized how good it was. I was constantly hearing iron targets where the CS1MX was silent or spitting with the discrimination at 5-7. After a short training, you will recognize iron quite well with the exception of large and heavily rusted pieces which would fool most of other machines as well.
Scanning the beach brought me a bunch of coins - there is no problem in the dry sand at all (except for bottlecaps, pull tabs and aluminium scraps:). As it is easy to dig on the beach, I am mostly searching it with lowest discrimination. Only after there are too many rusty nails, I put it back to the 5 or 6 position. Mineralised sand causes falsing and reduces the depth, however you will find all the shallow coins without any problem, the false signals are easily recognised from good targets. For the wet sand, there is a lot of falsing. You may reduce the sensitivity (I do not do that) and work more slowly and carefully listen (that is what I do). You will recognize a good target from the falsing after some time. This strategy brought me a silver ankle bracelet, a tiny silver ball shaped ear ring (around 5 mm diameter), a woman's golden wedding ring and a few coins in a very bad shape. To be honest, none of those was deeper that 4-5" (10 - 13 cm) and pinpointing without a pinpointer is tough - even an empty hole in the wet sand is falsing - and many times as strong as a regular target.
I will keep this detector, I sometimes lend it to my friends on a search. All in all, it is a great starter machine for the land and after some experience for the beach as well. In the US, Tesoro Compadre has a kind of cult status amongs its users. The CS1MX is easily on par with the Compadre and most of the times it is even deeper.
I will share a trick I have learnt with this machine. If searching with discrimination, try pinpointing the target without any discrimination as well. If the center moves considerably, it is a large piece of rusty iron. My guess is, that with the discrimination the detector sounds off at the edges. The "length" of the tone in all-metal will also tell you.