I agree with keff, take the Ellesmere road then either onto Ruabon and across to Llangollen, or cut back towards Whittington. The A5 between Montford Bridge and Oswestry has LOTS of speed camera vans, including on the overhead bridges!! Be warned...
The 1st bit from Shrewsbury is best avoided. There are a number of better side roads, try the A528 thro Ellesmere.
This is the best road Ive been on yet, the scenery from Corwen to Bethesda is spectacular and once you get to Holyhead the scenery is awesome. A lot of the road is national speed limit but it does go through a few towns so there are a few part where there is 30 mph speed limit but for 90% of the A5 it is national speed limit. There is also plenty of bends especially just past Corwen. I didnt see any police cameras when i did this. This is a must ride for any biker.
This is the view once you get into Holyhead