We're definitely working on some speed improvements for the finished version. Am I correct in guessing that you've got most of the PlecoDict data files stored on an SD or MMC card? Right now, whenever PlecoDict starts up it copies a few hundred K of data out of those files and into memory for faster access while it runs; in the final version, we're going to let you select an amount of storage RAM that PlecoDict can use as a permanent "cache" so that it doesn't have to copy that data over every time it starts up. This should dramatically reduce the startup time. We've got some other tricks we're working on as well.
And yes, we most certainly are planning to add a search button option in the finished version, along with a feature where the dictionary only begins a search after a certain (selectable) length of time passes without any further character input. Searches should be a little faster, too - actually a lot of the delay now is related to the font system, which isn't as speedy as we'd like it to be yet.