There's been a lot of discussion and general knashing-of-teeth over the decision of Sling to not support the iPad with the older Slingboxes including the Slingbox Pro, which up until now had been sort of the weird middle child between the older legacy Slingboxes and the newer Slingbox Solo and the pro-HD which officially replaced it. One thing I had done in previous writing here was to try to shed some light on why Sling might have made such a decision since Sling is pretty tight lipped on the technical details. To summarize, I discovered that older Slingboxes (and likely this includes the Slingbox Pro) used a Texas Instruments based Digital Signal Processor solution in order to digitize the digital/audio stream and prepare it for internet streaming. This solution is flexible in it's programming but because this solution is not an on-chip H.264 encoding/decoding solution, it simply doesn't have the horsepower to handle any kind of video past a basic 320x240 solution and it doesn't even do that well compared to H.264 solutions.
But for those of us who spent $300+ for the previous Slingbox Pro, even though I've had mine for the past 4 years, it seems weird to throw out a perfectly working piece of consumer electronics gear (nevermind the fact that many of us regularly do this with personal computers). I think the hard part for many of us is that none of us have a Slingbox Pro-HD to compare the Slingbox Pro to (or even the Slingbox Solo which is feature similar to the older Slingbox Pro). But one of my friends bought a Slingbox Pro-HD so I've been able to compare it to the Slingbox Pro that I already own.
First, I live in Nashville and my friend lives in Mobile, AL. It's hard to do a true apples-to-apples comparison inside my own house since on my gigabit LAN + 802.11n network, my Slingbox Pro regularly saturates the network at 4000+ kpbs per second which looks pretty good on the Macs and PCs I own. So I decided to do the test across town at my mother's house. Both of us have Comcast broadband connections and she has a 2008 circa iMac Core 2 Duo machine. I used the current Slingbox web plugin using Firefox 3.6.13 as the browser. I set both Slingboxes to watch the same ESPN HD Sportscenter broadcast which had lots of action clips, topic text on the left hand side of the screen and a bottom crawl.
First I accessed the Slingbox Pro from across town using the iMac. In the first several seconds, the signal was below 300 kpbs and the video was the familiar super-blocky mess I've grown to expect from using the Slingbox Mobile product on low speed networks like 3G or using the Mac or PC product from a lousy LAN connection like a hotel. Text was completely unreadable, either for the subject text or the harder-to-resolve crawl. As the bandwidth throughput got better, the action on the screen got better and the software was doing better on things on the screen that didn't change much, although the text was still a mess. Once I got around 1000 kpbs, things began to improve to the point that text was readable and the sharpness was coming into focus. But it still didn't look like the 4000 kpbs sharpness I saw on my LAN network at home.
Then I switched over to the Slingbox Pro-HD. Instead of a distance of a 10 miles, now I was doing 600+ miles but still within the Comcast broadband network. Immediately I saw a difference in low-bandwidth access. At 300 kpbs, the H.264 stream was much easier to make out and text wasn't the complete mess that the older Slingbox Pro was. At 500 kpbs, it was clearly identical if not a bit superior to the previous efforts 1000 kpbs streaming. Text was readable and action on the screen didn't turn the whole screen into a blocky mess while the encoder tried to catch up. At 1000 kpbs, the Slingbox Pro-HD was very impressive, rivaling what I'd seen with my Slingbox Pro doing 2000-3000 kpbs. 1200 kpbs was about the best this connection was going to do given the circumstances but it was clear that a LAN stream would likely be pretty close to delivering a true HD experience (at least for 720p).
I then later repeated the experiment with a iPhone 4 using a 3G connection (I don't own the iPad app). Throughput of the AT&T 3G network is not ideal at my house but still measures a respectable 1400 kpbs download speed. Both the Slingbox Pro and Pro-HD showed a decent picture on the iPhone 4, but again text on the Slingbox Pro-HD was easier to read (especially using cable box program guides) and action scenes from ESPN HD seemed to be better handled on the Pro-HD. I think the real difference would come out in lousier connections, like when I've tried to use in-flight Wifi to watch an NFL football game, or using 3G on an airplace tarmac when allowed by the pilot.
So again, is it worth the money to upgrade? If you are slinging in house on your LAN, you may not feel a real reason to do so unless you really hate doing the iPhone app on the iPad. But for those of us who travel a lot and rely on slinging with our iPads or iPhones (especially the higher-res iPhone 4), upgrading would likely solve a lot of the "hard-to-see" chunkiness of video, especially sports video. I've found it nearly impossible to read the sports scoreboard graphics on my iPhone 4 under less than ideal 3G streaming. This is much less a problem with the Slingbox Pro-HD. One other consideration is to "upgrade" to the Slingbox Solo. Although you won't get an HD stream on your local LAN, it pretty much does the same as the older Slingbox Pro and delivers better video quality to boot. And since the Solo is $100 cheaper than the Pro-HD, that and the Sling $50 upgrade gets that deal to easily less than $200.