I'm going to slightly extrapolate on what dhmholley said regarding knowing your users. While he/she brings up excellent points regarding "casual" users vs. power users and needing to be aware of those differences, I think it is important to keep in mind the shift in the workplace environment as more and more millennials enter the workforce.
The millenials are a generation that have grown up on technology and it's almost an after thought in their daily lives. If we can start to design internal applications that feel like the technology they use in their daily lives as opposed to your "old" heavy data entry WinForms layouts then it could help create an emotional connection to work. The idea is that it reduces that strict barrier between what they do at home for entertainment and what they do at work. This in turn may help extend the emotional connection they have with their devices at home to their job and make it feel less like "work".
There is plenty of information out there about how the millienial generation can't be bought, that they value intangible benefits over monetary raises and are always looking for the next best thing (i.e. little loyalty). So if internal applications can encourage that emotional connection to work then it may help address their intangible needs. I'm not saying this is always an appropriate design pattern but with this upcoming work force and the psychology behind it makes it interesting and thought provoking.
TL;DR: That was a long winded way of saying that you should still consider the contemporary and modern design patterns when developing internal applications. Chrome Add-ins have this similar applet layout, Windows 8 is Microsoft going in this direction as well.
As an aside, while your internal users may be power users and have the ability to master the system over time, a better design approach can help drastically reduce training costs.