Play sent me these by mistake, I actually ordered the Sony MDR-AS50G (which are earbud type but with a neckband), but decided to try these as they are water and sweat proof.
I want them for running and after three outings I have to disagree with the previous reviews saying they are not suitable for running.
Any in ear (without head or neckband) earphone is going to be prone to fall out when running. The 'silicone earbud' type such as these are the most secure (other than made to measure ones) of in ear types (as opposed to side on with neckband or just regular in ear) I would say. A lot also depends on your own ear size/shape I guess too!
I have been out for three 10k runs and they have stayed in fine (I am Mr sweaty when running!).
That said it is very important that you use the supplied clip and attach the cord to your top to minimise cord pull. The only thing I had to do was pull the right hand cord level from behind my neck now and again as it can slip and pull on the right earpiece (again, as any of this type would) when running.
Other tips would be to ensure ear and earbud are clean/dry before inserting so as to get a good initial 'grip' and use the correct size earbud (s/m/l supplied).
Both previous reviewers also mentioned hearing unwanted noises of cord rubbing against your clothing etc. This is again just a characteristic of this 'earbud' type of earphone. Because they seal off the ear canal completely and it affects the sounds you hear, but it is not noticeable when listening to the type of music and at the volume most people run to. If you listen to quiet music or music with long quiet sections or book tapes, then you will notice it, but again it is just the type of earphones, not the model in my opinion.
The sound quality/bass is very good. The bass response is I guess what most people want from earphones, and these have a decently low frequency response of 17Hz giving a distinct 'thump' at the low end.
They are not worth the 49.99 list price, but are a very good buy at play's 17.99.
If you think you need a more secure fit try something like the Sony's (which I have reordered, but yet to receive) with a neckband. Neckbands may offer a more secure fit, but the downside can be that they are not as comfortable for a lot of users. This is one of the reasons I kept and tried out the CX180's, I am glad I did because for me they stay in and I would recommend you do not rule them out for running.
My only grumble is the long cord. It would have been nice to have a short cord with an extension as some others have. This would work much better if holding the player or if you use an armband.