Yesterday was my first game session since the playtest was released, and my GM was gracious enough to allow me to try the whole thing out.
My initial thoughts are that this is going to be a solid system. Currently, our characters are all level 2, so that may have something to do with it, but I did not notice any of the potential problems that some have raised (specifically that it would be too complicated or not versatile enough). I can say right from the start that the targeting options were a godsend. Even at 2nd level, the ability to fire off a 2d4 at 2 targets (via Burning Flash and the MASS target word) makes you feel useful as a blaster, not to mention the delight of being able to target specific critters rather than worry about that Cone that is going to catch half of your party.
Our characters being at level 2 did cause some option deficiency from a multiple effect standpoint, but I would imagine that this is to be expected from a game balance standpoint. That being said, it is still fun to be able to hit an opponent with a little bit of (crit possible) damage along with a small de-buff. Looking at the list of words as presented, it seems that Weapon Focus (Ray) would be an enormous benefit, as would Improved Critical (Ray).
One of my criticisms is that the Mass target word seems a little overpowered for just a +1. While it was enormously useful at this low level, and is probably less so at higher levels, it seems that +1 is just not quite costly enough. Unfortunately, I don't think overall that it is worth +2 either. It should be fine, but in my mind it is something that should be considered carefully when designing new words, as there could be some abuse there.
A second issue that I had with the whole system was the CL requirement on Word Burning. If this is a game balance issue, then so be it, but I found in a few cases that I was wishing I had one or two more points for something truly specific to the situation at hand. Given that you can only burn one slot per day to fuel this, my opinion is that it would not be gamebreaking to offer it with no CL requirement.
Finally, to end on a positive note, this does not seem like it will be as complicated and weird as some people think. As a 2nd level Sorc, I had 5 known 0 level words and 2 known 1st level words. All I needed to keep track of all my options was a simple text document that had my Words known, the cost of each Word, the cost of each Target Word, and the cost limits for each level. I had a spreadsheet containing all of the Word information (hopefully, at some point, this will be used as part of an application to help with cost/effect calculations) that I used to look up specifics, but I didn't find that remembering the Effect Word effects to be any more difficult than remembering straight spell effects (the same being for saves/SR/duration/etc.)
Due to the bi-monthly nature of our game, mandatory overtime for some of our players, and the holidays coming up, I will probably not have a chance to work with the system again until after the new year, but nonetheless, I had a good experience with it from a low-level standpoint and look forward to the final release.
