Marantz PMD620, Tascam DR-1, and Zoom H4n.
The Sony PCM-M10 will be the cheapest flash-based recorder from Sony capable of recording 96kHz/24-bit stereo audio using either the internal electret condenser mics or an external mic or line input. The recorder has 4GB of built in memory and a MicroSD/Memory Stick Micro slot. This is the first time I'm aware of that any Sony recorder has accepted any form of flash media other than Sony's proprietary Memory Stick format.
The PCM-M10 is the first member of the PCM-xx family to feature a built-in speaker for playing back recordings. It also has a low-cut filter, digital limiter, and a 5-second pre-recording buffer. In other words, is has almost all of the software features found on the Sony PCM-D50 which is larger and has a list price of $599 (although it typically sells for $450 or more). In addition, the PCM-M10 is the first Sony flash recorder that lets you record in MP3 format. The PCM-D50 and PCM-D1 only record in WAV.
I'm going to go out on a limb and assume the primary difference between the PCM-M10 and PCM-D50 is that the new model features cheaper mics, preamps, and other components, although it is still made of metal, which makes this recorder more durable than some of the others on the market. The plastic mic jack doesn't look nearly as sturdy on this model as the metal one on the PCM-D50 though.
The Sony PCM-M10 is due out in October and will ship with a copy of Sound Forge Audio Studio Recorder Edition.The folks at Sound on Sound shot some video, which you can see below.