This review touched on performance, but it really was abysmal. Nothing was quite as painful as watching other people use the device; swipe gestures and touch points were frequently missed, the swipe-down gesture necessary to close or dock a metro app lagged behind by several seconds and took literally a dozen tries to successfully pull off, and even after installing the optional updates by going to the desktop control panel, I was still able to out-type the stock Mail application, using the touch cover at an abysmal ~10WPM. That was after waiting 5-10 seconds for the mail client to launch in the first place.
App support was the biggest offender, and I get that this is a short-term problem. That said, searching the app store for an SSH client and seeing nothing was a deal breaker. In the absence of useful applications, a terminal window that I could use to get somewhere to do actual work would have been great. Even in games, it feels like the strategy was all wrong. The usual suspects (Angry Birds, Fruit Ninja, etc) are there, but this would be my 4th or 5th time purchasing those games. Really don't have an interest in buying them again, and the original content under the New Releases section is really lackluster; apps that are still using the default Visual Studio app icon aren't uncommon, nor are apps with written entirely in different languages than the target market. The whole quality control angle seems sloppy.
If I could have installed another browser or had access to the Chrome web store, that would have been enough of a mitigation for app support, but those aren't options either.
The out-of-box apps are, understandably, incredibly Microsoft-centric. Couldn't change default search provider in Internet Explorer and the messaging client only had support for Live Messenger and Facebook. The app store currently has nothing available for music options (no Pandora/Spotify/etc). The browser is an option, but the Metro browser stops playing audio once the device auto-locks.
The speakers were really bad. With any level of ambient background noise, watching something on Netflix required my face to be less than a foot away to actually make out dialog. Was a common theme among other people using the device as well.
Touch cover was incredibly hit or miss and missed more often than not. In retrospect, I should have gotten a Type cover.
If the Surface had released with the iPad 2, it would be a competitive offering. At this stage in the game, though, it's competing with entrenched 4th generation and beyond offerings with years of developer support. Worse yet, it's walking into new tablets with specifications that are nearly twice as good for less money.
That said, the form factor of the Surface is incredibly solid. If someone sold a tablet with the Nexus 10 internals in a Surface form factor, I'd buy it in a heartbeat.