HDMI was supposed to bring the home theater world from the confusing age of multiple cables for audio and video (and sometimes multiple audio cables and multiple video cables) down to just a single cable from each component to your display. If your display doesn’t have enough HDMI inputs for all your sources, you need an HDMI switcher or a receiver which has an HDMI switcher built in. Then you need an HDMI cable from the each source to the switcher or receiver, but just one from there to the display. Fortunately, even some budget receivers now have HDMI switching built in (starting around $400), and there are good inexpensive HDMI switchers on the market like the XTremeMac HD Switcher I reviewed last year.
But what if you have two displays?
At least in terms of receivers, you’re in a completely different price category – no $400 receivers for you. The least expensive receivers I could find with dual HDMI outputs are from Onkyo and Denon. Onkyo’s TX-NR905 has extremely high end video processing, advanced room correction that smooths the sound at multiple seats, a ridiculous amount of amplifier power with THX Ultra2 certification, the dual HDMI outputs we’re looking for, and a price tag that ranges from $1500 - $2000 (assuming that you can find one in stock. It seems that they’ve been selling quite well). Unfortunately, only one HDMI output works at a time, and to change between the two HDMI outputs, you either must physically press a button on the front panel to cycle through the settings, or adjust a setting in the menu. Neither option is conducive to automation by a universal remote control which is a fairly common way to use a product in this price category. Denon sells the AVR-4308CI, which is also chock full of features, as you might expect for a product that sells in the $1800 - $2400 range. On the Denon, the dual HDMI outputs are driven in parallel; there is no way to select them individually. This is fine for some situations, but it means that whatever the source device is outputting had better be perfect for both displays if they’re both turned on at the same time (only one display gets to handshake with the source device through the receiver and tell the device what display resolution, frame rate, etc. it wants).
There are several HDMI switchers on the market with dual HDMI outputs, and they’re a lot less expensive than buying a new $2000 receiver. Accell has sent cables here in the past, and when I saw them at CES this year they were showing off an entire line of reasonably priced HDMI switchers, topping out at a 4x8 switcher – four sources hooked up to eight displays for those times when you want your rec room to look like a NASA shuttle launch. 
The Accell UltraAV HDMI 4-2 Audio/Video Switch is far more reasonable (4 sources to 2 displays), and lists for a very reasonable $299 when most similar switches start at $500; I asked them to send one over for review.
It wasn't perfect, but overall I liked it: it does one thing (switches HDMI signals) for a reasonable cost, and it does it pretty well, though with some caveats. It’s quite small and I had no trouble installing it. I didn’t have a high definition test pattern disc to use, but video quality on real-world material appeared unchanged by the switcher – Ratatouille on Blu-ray from a PS3 looked just as ridiculously good direct from the PS3 or routed through the Accell. The PS3 and my Panasonic projector often have minor handshaking dropouts when loading a disc and making its way to the menus; the instance of dropouts did seem to increase after adding the switch in the chain, but if so, the difference was minor and – honest – I may have imagined the increase. The switch automatically changes the input to whichever source device is on. Since my TiVo HD is always on, I couldn’t test that fully, but it did default to that input. Accell claims that the switch mirrors the source on both outputs (like Denon’s scheme above), but I didn’t find that always worked in the real world – I could usually only lock onto the source on one display at a time. It’s possible that there was a problem in the switch, but I’m willing to bet that it’s a glitch in the way my TV and projector handle HDMI signals or the difference in resolution between the displays (a Panasonic 720p plasma and a Panasonic 1080p LCD projector). For my intended purpose – watching either the TV or the projector, but not both at the same time – the Accell switch worked perfectly.
A small infrared remote control is included that has discrete buttons – and discrete IR codes for those who want to copy them into a universal remote control – for each individual input, power on, power off, and a toggle switch for selecting between outputs A and B. In a really nice touch, an infrared receiver cable is also included so that the switcher can be secluded behind a cabinet. The switch contains a signal booster for longer HDMI cable runs up to 82ft; I was not able to test this, as my longest run is 25ft. The switch is designed for HDMI version 1.2. HDMI version 1.3 is the latest and greatest iteration of the standard, and adds things like Deep Color which have not been implemented yet in any source material. For most people, there is little practical difference between HDMI 1.3 and 1.2, but if complete futureproofing is an absolute requirement, this iteration of the 4x2 Switch isn’t for you.
Accell isn’t the only 4x2 HDMI switcher on the market; Gefen makes one for $549 that has some additional functionality, such as splitting out the audio signal to a coax output, that could be extremely useful in certain setups. And budget cable outfit monoprice.com has a budget model with HDMI 1.3a compatibility for just $89 – I’ll be testing that one next. For $89, if it just turns on I’ll be impressed.
-avi