"Nearly everything" would have been the easiest answer, but I'll explain a little more I guess. You can take this whole comment with a grain of salt, since I don't know everything obviously.
I'll leave aside the call centre in Montreal since we don't work there and we don't really know their conditions there (well, they do have A/C and heat in the new office building...)
The datacenter in Beauharnois was the first one built outside of Europe, and even if there's 6500km between here and France, you'd think that a company that boasts about innovation and fresh ideas would think about this very fact on day-to-day operations.
Well, guess what, they don't.
It's actually amazing that the whole Canadian crew (not just the technicians, but everyone employed by OVH here in Canada) are actually performing just as much or even better than the people from Europe, and boy do we have the greatest conditions here.
Lack of proper tools, patches for firmwares not pushed here 'cause "what's that, Canada ? Dunno, where's that ?", obsolete building being repaired on a need-to basis. For those who didn't knew, the building was build in 1943, and it shows. Add to this little history fact that, here in the Montreal area, winter temperatures can go as low as -40°C , and 40°C (and worse) during summer, you get an awesome environment for servers. Yeah, they're water-cooled, but the building itself isn't isolated. Technicians are working in winter gear (we have to bring our own coats, gloves and hats, France apparently doesn't know it's cold here).
There's one thing every team here in the datacenter have in common: there's not enough people. Our supervisors are running all day long, and do an incredible job, but that also means we can't ask for help as much as we'd like, and there's a lack of encouragement for the work done by their respective teams (I can already hear the "a job well done is it's own reward"). There's no time for reviews, so you don't know if the work you've done is bad or not, which means that the bonus (there's actually a bonus, yes, based on performances) is often a mirage they'll mention, especially since they've set incredibly stupid goals that nearly no one reached.
Lack of communication between every team is also a problem (and I think the other reviews are proof enough). Not only are we often forgotten from discussion, but even between the teams here in Canada there's a severe lack of it.
Let's concentrate on the technicians now.
The pay is actually not to shabby, compared to other jobs you could have as a level 1, might be a little less great as a level 2 though.
Work shifts are 40 hours a week, on rotations. Day (6am - 4pm), evening (2pm to 12am) and night (10pm to 8 am), with three days between shifts to prepare for a new sleep cycle and eating hours. During the shift, they expect you to answer in a split-second, even if you're on break or eating (a switch that breaks down won't wait). You can take your breaks whenever you want, but more often than not you simply can't. It's cold outside ? Well, that's too bad, endure it. Enjoy explaining to other departments why the servers are having problems, they've never set foot in here. Some don't even know what -40 feels like (yeah, the temperature part comes back a lot with good reasons, who seriously expects a datacenter to be a giant ice block in winter and a sauna in the middle of summer ? Just watch how a Google datacenter works on youtube).
Bonus is based on quantity, not quality, which means the guys doing quick jobs and who won't take the time to fix permanently a problem are having a bigger pay than you if you work like you should.
Most of the job is hardware based, and is relatively simple. The thing is, OVH use a lot of in-house systems, which means everything you learn here is useless outside the company. Now, logic would dictate that in such an environment the company would want to keep its employees for a long time, and you'd be wrong. You're mostly stuck where you are, new jobs are rare and by the time you apply (remember the lack of communication ?) they'll give the job to someone else. There's also some new datacenters being built across the planet, and this might be a great opportunity to travel and get some experience, but be ready to leave everything behind for at least six months, if not more. If you don't have much here, this is actually great.
On a side note, there's also this weird mentality in the upper management that we own everything to OVH, that THEY'RE the ones that put food on your table and whatnot, and that you should be glad to work here, no matter how much idiocy you have to deal with. As another technician from France said, level 1 are nearly sub-humans, and non-existent. If something breaks, we'll repair it, and someone else will get the nice e-mail with congratulations.
Tl:dr (for level 1 technician, skip the rest if you don't have time)
Good pay, bad work environment, solitary work and terrible work shifts all around. Almost everything you see as a level 1 is useless outside OVH.
2/10, would not recommend unless short on cash.