Picked one of these up last week but not really had too much time to test it.
However, I have addressed the filter thread issue in a way that might be too extreme for some but here it is anyway.
I looked at the magnetic option and as clever as it is, it is let down by the fact that there doesn't seem to be any info regarding a release date and I didn't fancy just having this thing in a box waiting for that to arrive.
Before doing what I did, I rationalised it by asking myself two questions :
1) Did I envisage a time when I wouldn't want this camera to have a filter thread
2) Did I envisage selling it and if so to someone who would be put off by it having a filter thread.
The answer to both was a pretty firm No so I pressed ahead with my not particularly hi tech solution of adding a permanent filter thread with the aid of a step up convertor and some super glue.
As luck would have it, I had a 46mm-52mm step up convertor and the 46mm end is pretty much the perfect diameter to fit the lens housing of the RX100 and only adds a few mm of extra appendage to the camera. One advantage to that is that it does add a little bit of protection to the actual lens glass which is no bad thing.
[img]http://www.eoshd.com/comments/uploads/inline/20751/501bd8d41ae06_r1000filterthread.jpg[/img]
So, I now have an RX100 with a perfectly serviceable 52mm filter thread.
I've found the Cokin A series system to be a good add on for something like the RX100 as it gives you a slot for a circular polariser and three more slots for NDs and Grad NDs etc so its pretty flexible.
As the A series are pretty compact, it also feeds into the cinema camera in your pocket vibe !
Another big advantage is that they are reasonably cheap (particularly "compatible" ones such as 4 x ND at less than £20 on ebay) and you also often find people selling an entire collection on ebay for a bargain price.
[img]http://www.eoshd.com/comments/uploads/inline/20751/501bdb1e8dd17_r1000filterthread2.jpg[/img]
Of course I'm not just limited to using the Cokin system, so I just add the 52mm-77mm step up and can use my Lightcraft variable ND as well.
So, there you go, it might be sacrilege for some to start permanently disfiguring a brand new camera but I think the ends justify the means in this case as it makes it useable now rather than at some unknown point in the future and at less than a fiver you certainly can't argue with the price ;)