I live in Scotland and the river i know best is the Tay especially the section from stanley.
A definite pro is that one of the few rivers which is never empty

No surprises! You'll have features for anyone. Big smiles (or swims) for beginners and playspots for intermediate paddlers. Class is 2-3. However in lower levels there is not much to play in. Upstream of the put-in you'll find "the wall" which has a clean powerful eddyline. Good for tailies! (not that i manage to do one) Staying upstream the put-in is good if you're up for play but levels are low or medium.
In high and very high water running the river is great. Some spots have big waves and its just fun.
Be aware that there is a partly destroyed weir just below the put-in. Apperently there is a steel rod in the river right opening. You don't want that to stick in your body.....
Cons? be nice to the fishermen and make a big circle around them.
However, If you decide to do a trip to scotland i would recommend going to the westcoast.. more rain, more creeks and if you're sick of the water go for a walk.. There is plenty for all! But i'll post once i got to run the Etive(middle).. apperently the best boof training run.. if you mess up you turn up in a pool..Easy!
Tom