The 5770 is really the tipping point in the ATI Radeon HD 5000-series. It performs quite well in a single widescreen environment, and there are instances where it performs admirably in Eyefinity. If you frequently play older titles that aren't shader intensive, such as anything based on the Source engine (Half-Life 2, Team Fortress 2, Left4Dead), then the 5770 could well serve you in an Eyefinity environment. Even newer titles such as Batman and Dirt 2 can easily hit 30fps in Eyefinity.
All in all, the fact that you can get a playable Eyefinity environment for less than $200 is quite amazing. The 5770 is a card for the user who doesn't mind switching between single screen and Eyefinity based on performance. If you want a consistently playable (at or near 60fps) Eyefinity experience in every game, then you need to look at the 5800-series. However, if you're on the fence about multi-monitor, or you have a couple extra monitors you might hook up from time-to-time, the HD 5770 may very well be the card for you.
Since I've originally done this benchmarking (this review has been in the works for a while), I now have a the cards to test the 5850 and 5770 in CFX. I will be testing those in the near future to see if the 5770 provides a good stepping stone for a larger CFX build.
As I wrap up testing on the 5850 and 5770 in CFX, I will be producing charts that compare performance to total price. This will be the backbone of our forthcoming Eyefinity Buyers Guide.
Again, the 5770 performs very well in a single monitor environment, and quite well in Eyefinity. It does so with low noise and heat, and with low power requirements. We will shortly see if a 5770 CFX setup is worth the investment. Between the 5770 and 5750, I would recommend the HD 5770 for the extra $40. Based on the performance, it's quite amazing to see what a $175 card can now do. Considering the low power requirements, you shouldn't need to upgrade additional components in your system either.
The 5770 is an excellent mid-range card, and will allow the user to an excellent opportunity to try Eyefinity without extensive investment. I could easily see how this card could play out well in a college dorm environment - students are poor, and extra displays are as readily available as next door.