Among the beers I tried while in Belgium the previous week I liked most these two well-known brands. There are different brews of both brands and, as is usually the case with me, I preferred the dark ones. Leffe had a robust flavor, perhaps a nutty aroma and a rather sweet taste. Grimbergen, on the other hand, was only slightly sweet and had a smooth, even flavor. One characteristic of these brands is that they are always served in their own glasses.
Both Leffe and Grimbergen are definitely sweeter than the ordinary beers. I enjoyed them, but if you don't like any sweetness in your beer, stay away from them.