Well, I had planned to take my CSSLP in April but life got in the way, so I am shooting for more of an August timeframe now, after the book is written.
uCertify has a web client that I thought would work out well for me since I keep moving back and forth between different machines. I think they are pushing to the web to draw in tablet users, but either way, it works out well for me.
The web is a lot like the PC version in functionality. They have four test styles - the pre-assessment, the quiz, a regular practice test, and a new thing, Flash Cards, which I think are very cool. There are four study materials, too: the textbook, reports on your trials, a planner and the Final Test, which you should get a 95 on before you go take the exam.
The whole thing is implemented in HTML, and is occasionally a little choppy. I am running it in Firefox right now, and it is a little better than it behaved in IE10. It is very touch friendly and runs well on my Windows 8 slate.
The content is just as good as the PC version, and I feel very secure having it as my study partner. The flash cards are awesome - just like something you might have written for yourself in school: the term on one side, the definition on the other. I think this plus the official textbook will get me through the test. We'll see in August, though. The proof is in the pudding!
You can learn more about the uCertify web client at learn.ucertify.com.