I've been using the TMo Dash for about 6 months. I like it overall. The size and screen are great. The buttons make sense. The Joggrbar is fine once you use the freeware jog bar tweak program and mess with the registry a bit. Actually, there's a fair amount of registry tweaking that's required to make it useable, IMHO.
It's a bit slow, but I'm used to seeing the hourglass-equivalent. I came to my Dash from a Palm Tungsten C. So, I was a bit spoiled when it came to speed (400Mhz TC to the 200Mhz Dash), but then again, the TC was twice the size as my Dash. If I had to think twice about lugging my handheld around, then it was too big. With my Dash, I always have it with me because it's so pocketable.
The WinMob platform freezes too much. I reboot my phone 3-4 times a day on average. Mainly, I think it has to do with how the OS mis-manages memory. That's not the Dash hardware's fault -- that's purely WiMoSP from what I can tell.
Even with that, it's still a very good smart phone. I recently found a thread on dashsmartzone.com that described the registry tweak to increase the earpiece volume and that's made it a GREAT phone from a GOOD phone. I used my Dash while at a trade show (lots of ambient/crowd/conversation noise) and I could hear fine. Previously, I had to plug one ear and focus hard to hear in that sort of environment.
The Esmertec Java environment is fair overall, but just a bit quirky. I've actually adapted pretty well to not using a touch screen -- it makes for better one-handed operation really. The keyboard is definitely more cramped than my TC, but the unit's tiny compared to the burly TC. If I need to input that much information, I use my iGo/ThinkOutside Bluetooth keyboard -- 60-70 WPM input...no thumb board is going to keep up with that speed anyway.
The Camera is fair. My cell reception is pretty decent overall. The speakerphone is good for relatively quiet environments (in the car is fine), but not so good for louder/larger spaces. Bluetooth headset pairing is a snap and works quite well. Same goes with the BT keyboard.
Surfing via WiFi is waaaay better/faster than surfing on the Edge network. Although, if I'm in the car and need to access GoogleMaps...Edge is good enough!
Again, I like the Dash overall. I just wish it was faster (S620 has the same form factor and a 400Mhz processor instead...mmmmmm) and that WinMo actually managed the memory instead of mismanaging it as it does.
Still a thumbs up from me.