I have been using Modula for the last 6 months and it is a great gallery plugin for creating custom creative grids, in fact I think its the only one to have such a feature. Being able to size each image exactly as you wish is what makes this gallery plugin worthwhile.

Downside though is if you have lots of images, its easy to move one image and accidentally find all your images have shifted around, so be careful with it.

If you are not going to use the custom size grid, I would maybe advise against Modula though. It does not have the features of even some of the free gallery plugins in this case and you will find its use frustrating. Be warned the normal grid gallery will crop your image thumbnails and it is very very difficult to get it to show the whole image on each thumbnail.

But overall, if the custom size grid is an essential feature for you, then buy Modula, support is also excellent.