I only have a single OmniTouch and 5 cameras (two different brands). The OmniTouch is actually the only device on the network pointed at the MJPEG sub-stream URL, everything else is using the Main Stream which is h.264 and HD resolution (and supports 4 streams, as you said).
I will say, after using it for a week or so, the Foscam cameras seem to fail much more often than the Hikvision. They also generally take about 2 seconds longer to display the image when I click on them.
I also noticed that repeated requests quickly to the same camera will almost always result in just the Establishing Connection screen. For example, if I click on the little thumbnail view and before it displays, click on the full screen view it will almost always just get stuck on the EC screen. However, if I wait for the preview image to appear and then click fullscreen, it will usually work. This is especially problematic for popups since my motion sensor kept triggering the event multiple times quickly. I had hoped it would be a no-op on the OT7 when it was already popped up, but that doesn't seem to be the case. I finally just set a timer flag for motion which ensures it only fires once per hour. It's not perfect, but it definitely seems to have helped.
It just seems like the OT7 team needs to beef up their retry and connection handling a tad more. It's close, but not quite there yet.