I
rarely use mine for things that require prep. I'm strictly a "dump it & forget it" kind of gal.

But I couldn't live without it...there are certain foods that I don't like cooked any other way as I like my meats almost falling apart. LOL
I find it difficult to understand why your meal took so long in your mum's pot...unless you mean by comparison to "regular" oven cooking. Yes, it takes longer than that, but the "newer" pots (aka the past 15 yrs) cook much faster than the original ones did. I used to like mine for tossing things in & coming home after a long day at work to everything being ready...so there was no comparison in cooking time! But if you're standing around waiting for it, I think you'll be disappointed.
I prefer the oval shaped ones because I can put in a roast while it's still frozen without having to hack off a piece. LOL (I used to do that 30+ yrs ago.) Things just seem to fit better. I can even do a boneless ham in the oval - a big one with leftovers for the week.
I'm sure you've read in other threads that I use it to cook large quantities of boneless chicken that I then shred & freeze for later use.
It's the only way I'll make a beef roast....sometimes as a roast with potatoes & carrots and other times to shred for hot sandwiches with au jus.
We love it for pork & sauerkraut. (I use microwave potatoes so it's a no effort meal.) As kids, we always had hot dogs with this meal to cut costs on the pork. I still like them done that way, so I'll open the crock & toss in a pacakge about an hour or so before the pork is done.
I'm sure I'd use it even more if we ate a lot of canned soup. I see many, many recipes that call for dumping condensed soups in with meat, but that's too much fat for us. They always sound good, but I prefer recipes that add taste by spices instead of calorie-laden dressings & soups.