A couple of things spring to mind. I am thinking that the issue is that the chain doesn't climb smoothly/quickly onto the large chainring at the front? if that is the case - read on, if not - please ignore.

Firstly, don't gently stroke the paddle to change up. Make it a fairly brusque and definite change and at the same time ease off some but not all of the pressure on the pedals.

If that doesn't help then it's likely the cable is a little loose - or that the upper end stop screw has been set a bit conservatively. It's very easy to start messing around with cable tensions/end stops & get into a right mess. If you are fairly mechanical I would ask the mechanic at the shop to show you how it works (buying the small Park Tools book is also an excellent idea).

Finally, I'm afraid triples don't shift up front as smoothly as compact doubles do. And compact doubles don't shift as well as racing doubles. But you do get the benefit of a really wide range of gears (esp. very low gears). I would suggest you get very adept at both adjusting it & doing good positive changes. Much longer term a compact double is easier (& a little lighter) - but the shop should be able to make the triple work reliably if not perfectly crisply.

Good luck.