My housemate plays for Notts medics rugby, so I've picked up a couple of bits a pieces of info. Regarding quality, I'd say it's very variable; with medics rugby there are people who just play to train and maybe play some intermural matches, and at the other end of the spectrum we have some guys who were elite at under-21/18 level before Uni. How the medics 1st XV stack up against Notts Uni 1st XV, I do not know, but AFAIK some medic teams (Impy?) are significantly better than their parent Uni. Notts have 2 medic teams, the first team play BUCS matches at the weekend, the other plays on Wednesday. I've heard the teams referee to as clinical and pre-clinical but I don't know how firm that normally is, I know that my housemate was playing weekends by the end of first semester 1st year, but a pair of very good (now 5th years) in his position were stopping him from getting too much game time.
As with any medic sports club, they are designed to fit around the workload- Uni 1sts might expect you to train the night before an exam (because medic exams are at weird times from 3rd year onwards) but medics are far more chilled about people missing things for work related reasons.
The only other experience I have of medics rugby is looking after this guy following initiation in 1st year. That was no joke, and he believes that the ridiculous treatment of freshers is the reason why loads turn up to the first training sessions, but most pack it in following the welcome social. Again, it's probably the same everywhere, and if you've been playing men's club rugby then you'll know the drill.