They're all pretty similar. For general use, I'd probably recommend the HomeWorX. Its firmware is better than most and Mediasonic is still working on improving it. However I've heard the HW-150 model, with component and digital audio outputs, is no longer available, and their remote controls aren't very good.
If you're more of a tinkerer, the iView is a better choice. The 3500 (with those component outputs) is available and has a decent remote, and even the 3200 has digital audio. The only problem is you'll probably want to revert the firmware to an older version after you get it - their latest firmware has some problems. Luckily iView posts firmware on their web site, so you can do that without a lot of trouble.
The ViewTV has always interested me. Its remote looks nice. But I don't own one. There's a thread on this forum for it but I haven't seen a lot of info posted about it yet, so I don't have much of a basis to form an opinion about it yet.