I have the LG 34UM95 ->
http://www.lg.com/uk/monitors/lg-34UM95
Personally? I love it. Obviously being IPS, you get decent colour and viewing angle. Being the 1440p version is means a nice resolution boost, which looks impressive on video games and 4k stuff still looks fantastic through it. For gaming I prefer 1440p to 4k gaming because I can still get a solid frame rate without having to go down the route of SLI or a super high-end card. It was great when I was running a GTX 770 and it is even better now that I am running a GTX 980.
There are limitations, sadly. Now all video games are optimised for it. If you don't mind having the black bars, then it's like going back to a normal widescreen monitor. Some games can be tweaked and some games are ultrawide for content and 16:9 for cutscenes - see video below for transition between ultrawide and widescreen:
For me that's not a problem. Though I would ideally much prefer the aspect ratio to remain consistent.
And with gaming, here is a clip of me playing something (I was testing the Windows 10 recording tools, see how well they come out), I don't know if that helps simulate playing 21:9 in any way for you.
For workspace. I find actually it is great for programming. Especially as the one I went for is Quad HD. I don't have the need to alt-tab when coding. I can fit everything I need onto my screen at once and not feel restricted.
http://i.imgur.com/snTH7tX.png
The above is perhaps a little excessive, but gives an idea of how much space you can have. The above was just when I was testing ngrok, so I can use my PC as a host for testing my site on my mobile devices. Meant it used a little more space with an extra console window and an extra browser window.
And lastly, watching movies on it. There's some ways around this. Unfortunately movies, particularly on BluRay and DVD's have their black bars recorded in. So you've got movies like The Hobbit that are shot ultrawide and on a normal widescreen display get black bars at the top. On an ultrawide you get blackbars on the top and the side, unless you stretch it. The answer to this wasn't immediately obvious, because I tried to find a movie player that will allow me get rid of the black bars and play BluRays. Somebody modded Cyberlink Power DVD to have the option to scale to ultrawide. Fortunately, I did learn that there is a "Cinema" mode on my monitor, which stretches the display vertically to removes the pre-recorded black bars (so you still have to stretch). Which means I can watch things like that Hobbit on BluRay with the full use of my display without it feeling stretched. For stuff that's 16:9, stretching it isn't that bad on a 21:9, if you prefer it over having black bars on the side.
With things like Netflix that I can't stretch horizontally to fit my display. I have to go down to 2560x1440 and have the monitor stretch it for me to fill the display and then put it into Cinema mode. However, I find it all looks great. It would be nice if there was an easier way of doing it. Maybe a secondary cinema mode that stretches horizontally or custom modes so I can tweak it and save it for when I want to watch Netflix and have Cinema Mode for when I watch a BluRay.
And my monitor is capable of Picture-by-Picture and has some decent options. I have used it with my Chromecast before when also doing stuff on my PC, but given the distance from my router, I don't really get much use of my Chromecast when I'm with my PC, because the signal is often weak up here. But it's like having 2 non-widescreen monitors side by side without a bezel in the way.
I don't know what other manufacturers' Ultrawides are like. As with anything, always healthy to shop around and find what suits you best. Especially given ultrawides aren't cheap. I did research into mine before I bought it and specification wise, it was ideally what I wanted. But everybody's different.