I've been using the ZaggKeys Flex for about 4 days now (Comments marked "**Update, Mar 17, 2013" throughout this post reflect my more current impressions, almost a year in), and it's living up to my hopes. As I expected, it's a pretty small keyboard - a tad over half the size of a full laptop keyboard. Despite that, I don't have any trouble typing on it. I'm a fairly large guy (6'3" and around 250lb, with fingers to match), for what it's worth.
I've liked it well enough that I'm actually using it exclusively. I'd originally purchased it for use with a tablet that I have on the way; but I decided to give it a whirl when I'm on my laptop at the office. So far, I've had no reason to abandon it. Using it on a device other than a phone or tablet does raise some of it's drawbacks, though:
1. The "Sleep" or "Lock" key is positioned immediately above the "Delete" (backspace) key. That's far enough towards the edge of the keyboard that any inaccuracies in my typing from not being used to this keyboard size are a bit exaggerated. As a result, I've accidentally put my laptop into suspend mode a few times when I meant to simply erase a character or three. This can be a bit inconvenient, as usually I have to log back into my laptop before bluetooth resumes. Oops. Hopefully this'll become less of an issue as I acclimate to the board.
**Update, Mar 17, 2013: This has become significantly less frequent of an occurance for me. I do still occasionally paddle the "Sleep" key meaning to hit "Delete"; but it's far less frequent and I've made some changes to my laptop's config (switched from vanilla gnome3 to cinnamon) that now result in a prompt popping up when I make this mistake. Thus, the laptop doesn't suspend until I either hit "ok". If I hit "cancel", I'm back at my regularly scheduled programming. Absent this solution, the problem would still annoy from time to time; but not nearly enough to justify abandoning the board (to me).
2.The "Home" key is where you'd expect an "Esc". A "back" key, which functions in lieu of an "Esc" key, sits where you'd expect the right "Alt" key. I personally think these should be reversed. It may not matter much when working on a tablet, but when working on a PC you expect the key that functions like "Esc" to be in the top left corner of the keyboard. Putting it on the opposite end is counter-intuitive
**Update, Mar 17, 2013: I've completely adapted to this configuration
3. "Ctrl", "alt" and "command" keys. In order to accommodate both the apple world and the more PC-like android world, the four keys to the left of the space bar are (starting at the spacebar and moving left): the apple command key, a key that functions as either "alt" or "option" (depending on your mode), a "ctrl" key and a menu key. There's nothing particularly wrong about this, it just packs a lot of keys into an area I normally paddle with the ball of my hand (or with my "pinky" finger); so I find my touch typing crashes to a halt when I need to hit one of these keys, while I re-position my hand or glance down to validate my keystroke.
**Update, Mar 17, 2013: I've completely adapted to this configuration
None of these are deal breaking issues. More than anything, they fall into the category of "things to get used to". Aside from these small quibbles, I find I'm able to make a fairly reasonable 60wpm.
As a side note, for anyone who cares - I've been operating exclusively on an OpenSuSE laptop running Tumbleweed based on the 12.1 branch (Gnome3).
The reviews I'd read before purchasing suggested this keyboard could run for several weeks on one charge. I can't validate that claim yet; but so far I have no reason to believe it's not correct. (**Update, Mar 17, 2013: Claim confirmed! I rarely charge this board - maybe once a month, or so. Also, it functions fine while charging, so running out of juice is barely even an inconvenience)
All in all, I'm satisfied with the purchase; but I'll update this with my observations once I've actually used it with my new tablet
UPDATE:
I've now been using this keyboard almost exclusively for about 45 days. It's held up nicely. I've grown more accustomed to the key layout, so points 2 and 3 above have stopped being a problem for me. I do still find myself tripping up on point 1; but less frequently. Also, it's worth noting I've only charged the keyboard once in that 45 days.
**Update, Mar 17, 2013:
I'm still using this as my primary keyboard. I never revert back to my laptop's built in keyboard unless I've mistakenly left my Zagg somewhere else. Battery life continues to be excellent. I'd definitely advise purchasing this keyboard to anyone who's looking for a similar form factor.
Also, for the cave dwellers out there - I've switched from Gnome3 on OpenSuse Tumbleweed to Ubuntu 12.04 LTS on the same Dell Latitude E6520. No problems with this board on either distro.