I've had mine since launch and I absolutely love it. It needs more apps, that's for sure, but they will come. So far, I've been taking it to work instead of my laptop and it hasn't run me into any unexpected problems yet. I'll comment on a few particulars that either stand out to me or contrast what others have said;
Speed
It's been mostly a non-issue. I've heard people calling it laggy, but there has only been one circumstance I've found that in and that's if I'm downloading massive amounts of data in the background (for instance, allowing Xbox Music to download over 500 songs). Could be better, sure, but its a rare enough occurrence that its not an issue.
Peripheral Support
Its great to have a tablet that can take USB external storage so easily (and have complete access to the file system), plus the use of basic devices like keyboards and mice. The big surprise was to discover that Windows RT can install drivers just like any other version of Windows, just so long as the driver is complied for it. I've managed to install a USB Ethernet dongle (which Microsoft claim are not compatible) because the manufacturer provided a downloadable driver. So we have a future possibility of this being as adaptable as a standard Windows PC.
Adaptability
I took my Surface on a site survey last week. I used the rear camera to take site photos, then imported them into OneNote, used a capacitive pen to take notes, then sat down at a desk, flipped out the touch cover and wrote up a basic report like I was on a laptop. Then, when I got home, OneNote had synched to my desktop PC, where I wrote up a full report in Word. Technically, I could have docked the Surface to a keyboard, monitor and mouse and then done the full report on it, but I already have a high-end desktop at home and OneNote syncs seamlessly, so it wasn't necessary. I use the Surface as my desktop PC in the office, though. However, this scenario did pull up one particular dislike...
Camera
It takes pictures fast. It dumps them into an easily accessible file system, which makes it easy to make use of them in other applications. The picture quality is shit, though. It's like taking photos with a webcam. I've always been against the notion of taking photos with a tablet, as I've seen the nonces using iPads at weddings and concerts. USE YOUR PHONE!!! However, the site survey note-taking scenario actually showed me a good use for a camera on a tablet. Consequently, its poor quality irritated me no end. The pictures were omitted from my report, as they just weren't good enough. That's a shame.
Screen
I think the screen deserves a mention, purely because of the "not-retina" status of it. In reality, you won't notice it unless you are comparing side-by-side (where you will notice if you are looking for it). Unless you stick your nose against it, you are not going to see any pixels. The screen really does look great.