What you want to see is large packets, as large as your end-to-end infrastructure can support.
Personally, I would prefer to see more people fixing the infrastructure rather than accepting it as a limit. Install some Linux servers even if all they do is run an application layer proxy to turn the TCP stream from the LAN into something better suited for the WAN. They could use UDP, compress the stream, consolidate small MTU packets into big MTU packets, etc. I remember many years ago when a dentist asked me to help with an urgent problem on his billing system. The system worked fine but he split from his wife and had changed the corporate name of his dental practice. He needed to produce bills under the new name, but the software provider had gone out of business a couple of years earlier and there was no source code. Fortunately, it was a UNIX based application that used the print spooler for billing reports so I just inserted a shell script to change "Pleasant Valley Dental Inc." to "Dr. Smith Dental (1987) Inc." or some such. Fixing the infrastructure may also mean switching IP network providers to get someone who supports bulk data transfers between data centers with jumbo frames end-to-end.
Your application should be able to do that, potentially, and as other folks mentioned, your app can potentially be tweaked to open up multiple connections. I think there are also NICs which do something of this sort, but it's not something I've personally used (maybe others have experiences they can relate?).
Tweaking apps generally turns out to be heavy-duty stuff with lots of release control and testing. Also, the applications programmers generally have a poor understanding of network issues. If you can separate the applications stuff from the data transfer stuff, and tackle the network issues first, then you will have an easier time of it. --Michael Dillon