Ok, so here goes, sorry may be long!
We got a mini Schnauzer after spending lots of time with my BIL's one - I never knew much about them as a breed (other than they were the ones with the funny beard and moustaches!) but we knew that when the time was right for us to get a dog, we wanted a smallish one about the same size as her.
She is so lovely, such a cute personality, really well behaved etc etc that we kind of fell in love with the breed that way. We looked after her and another mini a lot as BIL's grandparents also have one.
We did a lot of looking around before we went to view a litter of pups, our boy is quite rare as he is a white one (very uncommon!) - I will try and add some pics on my profile so you can see!
We did loads of reading up on the breed, but to be honest, the more we read the more we felt this was the perfect breed for our lifestyle!
He seems to be very adaptable - very much as Turquoisecat has said above, he is quite happy to be walked twice every day but then wont moan if he doesn't go for a walk the next day. He quite happily amuses himself in the garden tearing about/snoozing in his bed.
We are really lucky in that the house we have recently moved into had a doggy door already built into the back door so he comes and goes as he pleases through that which means we don't need to worry if we are out for a few hours that he will need to be let out to the toilet. (would recommend this if you have a secure garden)
Agree about the wet food/beard! He will eat wet food and obviously doesn't like his beard being dirty so he wipes his beard off on the sofa! 
He is generally great with adults/strangers and to be honest he hasn't been around kids yet on a regular basis (Just DH and I at the minute, no DC of our own) but any that he has encountered he has been great with - he goes a bit shy when people approach us in the park for example, he almost looks to me for reassurance to go to new people, but once people talk to him/stroke him/give him a bit of fuss etc he is very friendly. Kids seem to love him!
I had read that they are very vocal/bark a lot. He does a low growl and sometimes lets a bit of a bark out if he sees people walk past our front window for example. (the front of our house is directly on the path so people do walk up right by the window) He will stop as soon as we acknowledge him for letting us know someone is there. But in general he hardly barks. (other than when the hoover is on!)
He does make a bit of a racket with squeaky toys though!
Pros:
Doesn't malt or have that doggy smell which is fantastic!
He's very affectionate and will quite happily sleep on our bed with us or fall asleep on the sofa cuddled in to us.
Seems quite happy to be left alone - he doesn't whine as you are leaving, that kind of thing.
He goes crazy with excitement when you get back though, which is really funny as he has recently started doing a running jump up into your arms when he's super excited!
Very quick to learn and teach at home. I taught him sit, lie down, stay & recall within a few days before he was allowed outside.
He picked up toilet training and using doggy door exceptionally quickly too!
He's such a little character - really makes us laugh. Everybody loves him.
Cost of food, treats, toys etc has barely been noticeable. He was weaned by the breeder onto beta puppy which we have kept him on, costs about £5.50 a bag which at the minute lasts around a month.
He has been great in the car - first few journeys he wined a bit but now he will happily curl up or sit on my lap if I am a passenger, and 9 times out of 10 will fall asleep.
If I'm driving him somewhere on my own I usually bring his bed and he will settle down in that in the passenger footwell.
This may just be him though, BIL's is fine in the car now, but when she was younger she would be sick every journey without fail!
Cons:
He does get easily distracted on walks, he suddenly appears to go deaf when there are other dogs around!
At the weekend we took him for a long walk with BIL's schnauzer and my brothers Labrador.
He just would not give up with the lab - showed no interest in the other (female) Schnauzer but kept trying to play and jump (and hump!) the lab who is male, who was getting annoyed at him!
He was just the same with PIL's female dog - he ran around and played with her all day until he was exhausted but still wouldn't give up!
He likes to chew anything soft/fabric - tea towels, shoes and socks seem to be the favourite! (Any shoes left out in the hallway are fair game!)
Luckily he only chewed a few hard things such as the wooden handle on a chest of drawers and the corner of a low level kitchen cupboard.
It's not as bad now his puppy teeth have fallen out but he used to be pretty bad for nipping and claws for scratching when he was younger - DH and me had scratches all over our arms for the first few months!
He also used to grab your trouser legs/sleeves in his mouth and pull when he was a young pup - he put holes in a few of my clothes!
He has calmed down with that now though.
The grooming has not been too bad so far - we have paid a groomer to do it as I don't feel confident doing it myself yet.
He is 6 months and he has had one full groom which cost £35 and a puppy groom which was £15 - just for feet, face, bum etc but not body or legs.
I think we will start doing it ourselves though.
He needs brushing every night ideally, which is ok if he sits still on our lap while watching TV!
He has had 2 rounds of (expensive!) ear drops from the vets as he keeps getting ear infections, most likely due to the hairs in his ears which you have to pluck out on a regular basis. This is a bit of an issue as he hates you toughing his ears now so have to try and do it when he's really sleepy!
He did go through a spell where he would get really horny and try to hump your arm in the evening - it was like clockwork every night but that has lapsed a bit now, he maybe tries to hump once a week! (but he is getting fixed next week so may be even less then!)
Only other negatives I can think of are:
Vets bills and insurance expensive, and we have a few stains on the cream carpet from when he was toilet training but that's nothing to do with schnauzers as a breed!
Please ask if you have any specific questions and I will be happy to answer them - over all I would highly recommend schnauzers as a breed to most people - they do seem to be very adaptable. Ours has fitted into our life very well without making many changes or sacrifices. That may have been quite different if we had DC though, I don't know?
Sorry for the huge post!