Everything is terribly slow
Part of this is because a lot of the UI and the Activities (applications) are written in Python. I understand that the goal of tinker-ability is trumping the desire for a snappy UI, but I fear that children (who aren't after all, known for their great patience) will get bored when they try to do something, and all they get is a blinking icon on the screen for a minute or more.
A co-worker says that he pulled his out of the box, turned it on, tried to use it for a while, decided it was unusable, and put it back in the box. I don't think it's that bad, but performance is definitely an issue.
One of the first things I tried was launching each of the activities, to see what each one was. That lead to the discovery that you really don't want to launch multiple activities at the same time. It was probably 5-10 minutes before the laptop was responsive again. They ought to consider throttling this in the shell, because I'd bet your average 8 year old is going to do just that when they use it for the first time.
Given that Psyco exists, I don't know why it's not installed on the XO to begin with. I couldn't find any indication on the OLPC Wiki that anybody had actually tried it. I'll try building a version and enabling it for a few applications to see what impact that has.
Great wireless sensitivity/range
I haven't had a chance to use the mesh networking features yet (due to lack of another XO, or a School Server to hook up to. But the standard 802.11b networking gets a substantially stronger signal than my conventional Dell laptop does.
Lots of features are still "to be implemented"
Totally understandable, I think. The hardware seems to be pretty well worked out, the software is just lagging behind (and who hasn't seen that on a project?). For example: there are about half a dozen keys on the keyboard for various special features. about half of them do nothing at all. There's a "view source" key combination, which doesn't do anything, presumably because the "Develop" activity isn't finished yet. So much for "easy to tinker", though...
Relatively clean User Interface
I admit it - I'm a fan of minimalist UI "chrome". I liked Nextstep, I liked the old Mac OS, I even liked CDE. The modern UI trend toward glossy reflective surfaces and transparency effects feels like a major step backwards in usability to me.
The OLPC "Sugar" interface is largely monochrome, and very simple. Presumably at least part of this is due to the limitations of the system (especially the requirement to be usable in black-and-white mode), but overall, it's pretty pleasing.
The camera and microphone work well
I can't wait to see what the kids will do with this. It's only camera-phone quality, but I think that'll be a popular feature.
Many of the activities are a little impenetrable
Unfortunately, many of the included activities are a bit hard to get started in. The music stuff is particularly bad. I understand that a full user-manual for these applications is a bit much to expect, but trying to "drive" a multi-track sequencing application without any documentation or online help, and with only icons in the user interface, can get a little frustrating.
Too many programming environments
The standard install comes with Etoys, Pippy, and TurtleArt - development environments for Squeak Smalltalk, Python, and some kind of "graphical" language, respectively. Rather than three different programming environments, I would have liked to see more "out of the box" usable software.