Lightweight, functional and cool; jury's still out on the Sonivox DVI.
My Vortex Wireless was purchased from Sweetwater by a friend as a gift. It feels fairly well-made, but it's not a tank. While it won't fall apart if you look at it wrong, I would advise treating it gingerly; it's a keytar, not a tennis racket.
The key action is similar to that of a semi-weighted synth like the Korg M3-61, but with a touch more springy resistance. It's a little on the loud side, too; you wouldn't want to use this in a recording situation where there are live mics in the room because the bleed would probably drive the engineer crazy.
What blew me away the most (so far) is that when I plugged in the wireless receiver (it's a USB dongle about the size of a pack of stick gum), My Sonar X3 recognized it IMMEDIATELY.
Translated: It. Just. Works. I didn't have to load any drivers or anything. I was pushing my Triton Rack via MIDI within seconds.
The pitch wheel is conveniently located, but on my unit, the movement felt like it had some resistance. It didn't bother me, but it felt a little sluggish. The data slider also felt stiff. I love the aftertouch, however, and the accelerometer is the embodiment of coolness. I also enjoy the LEDs on the tip of the handle, though I worry about their effect on battery life.
The only reason I haven't given it a solid 5 stars is that I have not yet been able to download the Sonivox DVI software. The process involves visiting an page on Alesis's website that is carefully hidden to find the download link (the software does NOT ship with the unit, contrary to anything you may have read or heard). You have to go to the Vortex page on the Alesis site, and then down into the FAQ page to find the link -- raspberries to Alesis for making the process as clear as mud.
Anyway, once I found the link, it took me to the Sonivox site, where I put a modified version of my serial number, only to have Sonivox tell me it was invalid.
Kudos to the fine folks at Sweetwater, though; they're helping me get it all sorted. I just hope the software is worth it once I finally get it. Despite the hassle, I only docked a half a star for it, because I have two hardware synths and close to a dozen virtual synths I can push with the Vortex, so I'm not out anything if the software proves to be a bust.