While this special does have something to offer to fans of the series it also partially disregards what made the main show so enjoyable in the first place. If you weren't a fan of Toradora! to begin with this probably isn't worth watching.
Review in full:
Toradora!: Bentou no Gokui is a zany one-off episode that focuses on Ryuuji early in the series. It shows a deterministic side of him that doesn't come up too often in the main series and gives the viewer a better idea of who he is and what drives him. However the plot feels a tad forced in that Ryuuji would have to be triggered pretty hard to push the episode's main dilemma like he does if we're going by what the main show told us. Within the main show he typically doesn't become competitive for its own sake, but here that's about all that can be drawn from the situation.
The way the main joke repeats itself doesn't make it as funny as the comedy in the main show either. In fact I can't recall any episode in the main show that recycled a joke as its main premise throughout its duration. It also doesn't help that most of Toradora! relied on and was seemingly built for story arcs that lasted 2-3 episodes. Perhaps this story could have been better if it had more room to develop. While the many characters present are generally themselves and the conclusion to the episode is nice, the episode as a whole just feels off-kilter.
Discussing the meaning of bentou under the blooming sakura is such an anime land thing, but it also sums up the general tone of this episode.Lastly, Bentou no Gokui's general production quality is simply good enough for what it sets out to do. The visual style is no different than Toradora! ever was, but there aren't any moments where particularly interesting camera angles or special animation changes are used like they were in the main show. At least the sakura scene was nice. Meanwhile the voice acting is just as lively & expressive as ever, but the episode sounds somewhat empty as far as music & SFX are concerned. Of course both are entirely reused from the main show, it's just applied more sparsely than before, which is not to Bentou no Gokui's benefit.
Verdict:
It's a good thing they decided to skip out on this story in the main series as doesn't fit very well with the rest of it and would have thrown off the show's pacing. It's worth checking out if you wanted more Ryuuji though.