Does anyone have any experience or advice on HDMI matrix switchers?
'Seems like the answer to switch a number of HDMI devices amongst two or more TVs (in different rooms, that might be used at the same time), but they also seem a little new yet - various brands, not easy to tell quality or limitations yet.

I haven't used any matrix switchers. They have been around for quite a while, but they can be a bit quirky because of the way HDMI operates (particularly HDCP and display EDID). If I were in the market for one, I'd probably have to do a good bit of research before making a purchase.

I have been using an Oppo HM-31 for about two years now without any problems.
Unfortunately they no longer offer them.
You might be able to find something on E-Bay or Audiogon.

The HM-31 doesn't have multiple outputs. It's a good switch, though - I've got one, too.

Thanks for responses! There is not much out there on which to do good research...so in the end I needed to take an partially-educated gamble. I ended up buying a "4X2 HDMI Matrix Switch w/EDID Learning & IR Routing" from hdtv supply. So far it has been working well - but there definitely was a lot of ~tweaking required to get everything to work properly. I have one last little issue that I think I have fixed...after a little time there to prove that it is fixed (including Wife Acceptance Testing) I will post a little bit more here about it.

So just to complete this for someone's future reference, especially since at least when I looked there is hardly anything out there, instructions and so forth with the devices are horrible, etc.....a HDMI Matrix switcher is a good thing. I would not recommend this device to a novice / non-hobbiest (unless you plan to be their support department and are good with that), but for anyone reading this I would recommend giving it a try if you were like me and looking for way to share HD HDMI across multiple targets (e.g. "my" DVR regardless of what TV I'm on).

It took some playing with and perhaps it should be noted that for much of my use I'm only worried about 720p and not too worried about particular sound formats, but in the end this solution has been very reliable and very useful. My sources through this device are two DirecTV HD DVRs, a iScan VP20 (for legacy upconversion / HDMI translation of some sources I want shared - e.g. DVD changer), and an OPPO BDP-83. My targets are a relatively new family-room 1080p TV and a relatively old 720p projector in the HT (the sound end of the projector is an optical out to a 990). Note that the line out to the TV is a 60ft run without any additional amplification. I leave the matrix switcher on all the time. It can send any source to any target and can also send a single source to both targets. My sources and targets are only on when they are being used...but it has been okay if stuff is extraneously left on too. Switching targets is about as fast as it takes to change a satellite TV channel (which exceeds expectations I had from research). The TV switches flawless every time, a source-switch from the the projector sometimes takes a little longer for the system to figure out what is going on / adjust to the the new signal/source.

Two lessons learned are 1) when you are first powering the unit up it is best to have all sources and all targets turned on so the appropriate base HDMI handshaking can occur and get noted by the switch and 2) in the case of my unit where there does not appear a way to give the devices rules on how to process "conflicts" in HDMI capabilities (e.g. my projector is both a lower HDMI spec than my TV and it of course the projector does not process sound), put the most important or "highest" capability target into output 1. I've found in doing this I have rarely (if ever) run into a circumstance where the projector couldn't handle a signal (nor where I was getting less to the TV than I needed / cared about at the time)...but if I had the projector in the primary output the unit would at times dumb everything down to the point that was no longer acceptable for the TV (e.g. dropped sound, and when that happened I never found a way to recover other than restarting the unit).