Here is what you are getting for that extra $200 dollars.

Screen...
1) 640x480 screen resolution
2) Superb contrast, brightness, and color
3) Wide viewing angles much like a plasma display
4) Very responsive touch screen
5) Flush-mounted display which not only looks fantastic, but makes for easy cleaning. The TSU7500's screen has the bezel around it which makes it a pain to clean the screen. Dirt and grim are always building up around and under the bezel.
6) Landscape orientation which I now favor after coming from the portrait orientation used by the TSU7500.

Hard buttons...
1) Page up and page down hard buttons are now programmable.
2) 5 firm key hard buttons versus only 4 with the TSU7500.
3) Power button, a new hard button which I find makes the perfect Home hard button versus the actual Home hard button grouped over by the directional pad.
4) The OK button is now in the center of the directional pad.
5) Hard buttons automatically backlight when any given hard button is pressed. You can also set the timeout for the hard button backlighting via the settings pages of the remote.

On-screen...
1) Pronto TrueType font.
2) Anti-aliased text once downloaded to the remote.

For me the two items above have been a godsend. With my TSU7500 PCF nearly all text was graphical text created in Photoshop due to the text used by the editor and remote looking so horrible. Now that I have the Pronto TrueType font and anti-aliased text I no longer use graphical text. Just using text via the editor. This saved me a ton a time when working up my XCF. The only exception to this is my DVD Juke menu screen which is a graphic.

3) The pressed state of a button remains showing on screen while said buttons action list is being executed.
4) Accessing the settings pages in the remote does not wipe out the browse backwards stack.

Extenders...
1) The RF carrier is now WiFi over standard RF. This is huge. The TSU9600 actually has to establish and maintain a connection with the extender or it won't send data. I use a RFX9400 in conjunction with the TSU9600. Over the past 8 months or so I've found performance to be ultra-reliable in Stand-Alone Mode from 60 plus feet out.
2) Two modes of operation available, Stand-Alone Mode and Network Mode. Stand-Alone Mode (Ad-Hoc) is where the remote and extender communicate with each other directly over WiFi. Network Mode is where the remote and extender communicate across your wireless home network, the TSU9600 talks to your wireless router, from there your wireless router talks to the extender either wirelessly or via ethernet.
3) Addressable IR outputs which allows you to control multiple devices which contain the same codeset independently without having to use an additional extender or integrate an IR routing solution into your setup.
4) The RFX9600 extender specifically brings RS-232, relays, and power sensing into the mix.

The Editor, PEP...
1) Simulator opens instantaneouly and can be launched to start on any given page in your configuration file.
2) Configuration file downloads to remote very quickly. Much improved over PPENG.
3) Sound support. Custom sounds can be added for use with your configuration file.
4) Many of the settings for the remote are now made in the editor versus the remote itself.
5) Configuration files can no longer be uploaded from the remote to the editor which protects ones work.
6) PackAndGo files are now supported. A PackAndGo file is a stand-alone executable version of your configuration file which can only be downloaded to the remote. It can't be opened in the editor. This file type is a great way for custom installers to provide file updates to their customers without having to give said customers the actual configuration file which could be shared with others. Again, this serves to protect ones work while at the same time making it easy for the customer to update their remote as the editor does not need to be used. In my case I've decided to not make my actual TSU9600 configuration file available for download as I have with my TSU7500 file. If you have access to a TSU9600 you can check out my PackAndGo file however. More details on my TSU9600 PackAndGo file including a download link can be found here.
7) Pronto scripting language with 2-way communication over RS-232 or TCP/IP. To learn more about this go here.

Additional items...
1) The remotes processor is much faster than what is used for the TSU7500. Page changes happen very quickly as a result.
2) IR is sent much faster while at the same time being sent more reliably.
3) Charging base angles the remote towards you allowing for easy operation while it's docked.
4) The remote is reset by pressing various hard buttons down at the same time. This is a much better design than what we had with the TSU7500 where you have to take the back cover off the remote to access the reset switch.
5) There is a power switch on the remote allowing you to completely cut power to the remote. I find this particularly useful when I'm taking the remote with me to demo for a client.
6) A diagnostics screen is available by pressing down a combination of hard buttons.

I'm sure there are some things I'm leaving out. The above items are the ones I find most substantial anyway over what the Pronto NG line of remotes offer. As you can see, you don't have to have a complicated setup to take true advantage of the TSU9600. At the same time, the TSU9600 opens up some nice options for you if your setup becomes more involved later down the road. Also, in case you did not hear the Pronto NG line has been discontinued. That being the case, I doubt we'll see additional firmware/software updates for the TSU7500. There are a couple new remotes coming out however, which maintain the portrait screen orientation, but add many of the features and technology we have with the TSU9600. Check out this post for more details.