I find Primark jeans to be very poorly made.
It's hit and miss if you don't select them well. The ones that are about £9 CAN be good quality, sometimes. You just have to pick a few that you like, try them on and you will instantly know which are the well-made, wash-enduring ones. Some of my best jeans have come from primark, whilst I have £40 ones from Burtons that look like
Star out swearing fully please. von. if they aren't washed and ironed after every wear. On the contrary, some jeans I have bought from primark without first trying on have been poorly made.
Imo primark is awesome for the £3 tshirts. Get the inconspicuously designed ones, in natural colours like grays, and they are really good. I personally wear primark clothes on a day to day basis, and switch to a designer slim fit shirt/tshirt when I want to go out on the town. I like to wear expensive shoes and jackets, however, because I feel they are the two items of clothing cheap clothes stores can't do well - and you don't have to replace them often.
If you're a man, it shouldn't take more than a few minutes to get what you need, because men's sizing is easy. I'm Small Tshirts and 30" Waist, so I walk in, grab 5 t-shirts that look (and feel) good, pick a few pairs of jeans I think will last - try them on and select the best - and off I go. Costs me about £30 every 2 months, and I look no worse than anyone that shops at Top-man/Burtons/Next/Whatever - mainly because I like to spend £100 every 6 months on a pair of Skate shoes and a loose fitting, good quality jacket I can wear pretty much all the time.
Primark is amazing and cost effective, but I wouldn't use it for everything. That's just me, but I think if you selected all your clothes from there with scruitny, you would look fine and save a lot of money. After all, some items of clothing have more of an impact than others, and it's your body/face that impacts your 'look' the most. I know people that look awesome in their £10 Primark outfit, whilst people that look like crap in their Jack & Jones £200 outfit.