Hi there,
I moved to Llantwit Major from Cardiff with my partner in July this year as I really wanted to be nearer the sea.
It's a really lovely little town, it's got a decent number of shops and facilities - Drs, dentists, leisure centre etc and so far the people seem really friendly and nice; apart from the lady in the post office- she was super grumpy and rude when we didn't have ID for picking up a parcel!
Anyway, the nicer areas are mostly in the west of the town. From our househunting experience we decided to avoid the area between Eagleswell Road and Bedford Rise and around Cardigan Crescent. They're by no means horrendous just the less nice areas but the house prices reflect this!
The old part of the town is the westernmost and has the loveliest houses, sadly we couldn't quite afford that bit so we went for one of the modern estates in the northwest.
The best way to get a feel for it though is just to come look at some places, there's three estate agents in town, Anthony brown, chris Davies and make your move, the latter were pretty rubbish and we gave up on them- they never had keys or replied to our messages.
Things that drew us to the town- it's less than an hour to Cardiff by car and train (yay a train station!), it has a beach which is rocky but beautiful and there are sandy ones nearby, the town has good facilities and schools and the surrounding area is really beautiful.
The town itself has a large Co-op and a Filco (a local supermarket) which between them have plenty for everyday food and essentials. There's a pharmacy, travel agent, Greggs, off licence, health food store, and several independant shops - hairdressers, jewellers, optitions.
If you need some bigger shops Bridgend has a giant Tesco and lots of other major chain stores only 15min by car away.
Hope some of that helps! If you have any other questions I'll do my best to answer them 
So far we are loving it here!